(navigation image)
Home American Libraries | Canadian Libraries | Universal Library | Community Texts | Project Gutenberg | Children's Library | Biodiversity Heritage Library | Additional Collections
Search: Advanced Search
Anonymous User (login or join us)
Upload
See other formats

Full text of "Experimental Electricity Course in Twenty Lessons"

Google 



This is a digital copy of a book that was preserved for generations on Hbrary shelves before it was carefully scanned by Google as part of a project 

to make the world's books discoverable online. 

It has survived long enough for the copyright to expire and the book to enter the public domain. A public domain book is one that was never subject 

to copyright or whose legal copyright term has expired. Whether a book is in the public domain may vary country to country. Public domain books 

are our gateways to the past, representing a wealth of history, culture and knowledge that's often difficult to discover. 

Marks, notations and other maiginalia present in the original volume will appear in this file - a reminder of this book's long journey from the 

publisher to a library and finally to you. 

Usage guidelines 

Google is proud to partner with libraries to digitize public domain materials and make them widely accessible. Public domain books belong to the 
public and we are merely their custodians. Nevertheless, this work is expensive, so in order to keep providing this resource, we liave taken steps to 
prevent abuse by commercial parties, including placing technical restrictions on automated querying. 
We also ask that you: 

+ Make non-commercial use of the files We designed Google Book Search for use by individuals, and we request that you use these files for 
personal, non-commercial purposes. 

+ Refrain fivm automated querying Do not send automated queries of any sort to Google's system: If you are conducting research on machine 
translation, optical character recognition or other areas where access to a large amount of text is helpful, please contact us. We encourage the 
use of public domain materials for these purposes and may be able to help. 

+ Maintain attributionTht GoogXt "watermark" you see on each file is essential for informing people about this project and helping them find 
additional materials through Google Book Search. Please do not remove it. 

+ Keep it legal Whatever your use, remember that you are responsible for ensuring that what you are doing is legal. Do not assume that just 
because we believe a book is in the public domain for users in the United States, that the work is also in the public domain for users in other 
countries. Whether a book is still in copyright varies from country to country, and we can't offer guidance on whether any specific use of 
any specific book is allowed. Please do not assume that a book's appearance in Google Book Search means it can be used in any manner 
anywhere in the world. Copyright infringement liabili^ can be quite severe. 

About Google Book Search 

Google's mission is to organize the world's information and to make it universally accessible and useful. Google Book Search helps readers 
discover the world's books while helping authors and publishers reach new audiences. You can search through the full text of this book on the web 

at |http : //books . google . com/| 



Experimental 
Itttvitit^ Course 



IN TWENTY LESSONS. 



GERNSBACK and H. W. SECOR, E. E. 

Authors of "THI! WIRELESS COURSE," etc. 



1X~ 




WITH ILLUSTRATIONS. 



THE 

EKIMENTER PUBLISHING CO., lad 

FULTON STREET, NEW YORK 



1916 



'■"Wl 



Copyright by 

THE EXPERIMENTER PUBLISHING CO., Inc. ■: 

1916 ^ - 



AU ^• 



Rer 



I Experimental 
Electricity Course. 



LESSON No. I. 

"ELECTRIC BELLS, BUZZERS AND 

ANNUNCIATORS." 

ELECTRICITY, when utilized for signaHing purposes, 
generally involves the use of electrical belis, buiiersi or 
annlindatoi's, and so these apparatus will be described 
in order; also the besC metbods to ptirsue in properly 
wiring for same. 

It is advisable, perhaps, to start with a description of 
the ordinary inbraling bell. The action of it is very simple, 
and ma:^ be the more readily understood by looking at the 
schematic drawing, Fig. 1. 

In this drawing are shown the various parts of the sim- 
plest bell circuit. Included in the circuit are: the bell jtse]/, 
of the vibrating type; the battery, of one or more cells, ana 
a push button for the control of the bell. The bell acts i^on 
Ihe principle that whenever an electric current, as from the 
battery here shown, passes through a coil of sevefal turns 
of insulated wire, there will be produced within the coil and 
abc'i*. it, an electromagnetic field of force, as it is terrded. 

IK^^.H^^I ■ ~ . ... 



^; 




t nlilBtrated, There are two coils ... . ___ __. 

tain but one. Now, it the push button is pressed, 
_.._ jontact springs in it are brought together, maltillg 
K electric circuit, through which the battery current passes. 
Jit BO on around through the electro-magnet coils on the 
mn frame of the bell. The iron cores of the magnets become 
l^denly strongly magnetized, attracting the soft iron pivoted 
Inaturc, which carries the gong hammer. When the arra- 
^re 13 thus attracted, and drawn forward, two things hap- 
lat — first, the hammer hits the gong, giving ou.t a, s^^wiV, 
•nd, the contact spring carried W "Ont a.im.i'w.'t^, 
intact or leaves the contact sctt-w aivo-*^ '■" ^^^ 



..^ ;^ ^ cad 



The consequence of (his is. thai the »ri 

er attracted became its torwafd ttniveni't 
battery circuit, and no current traverse- 
Hence the armaiure, whicli is normally I 
magnet core^ but against the oontiict sm 
once flies baeV to this pojition, or nwiy i: 
«0on as this haftpena, bbwever, i' 
more completed, the tnagncls .n 
lure is again attracted, strikiiu' 
push butlon is depreasi-d, thi; a< ;, 
vibrsfting- at a high rate of speed, ^.. , 

ringing of the gone- The number oi . . . . 

the action of the armature are easily regulated by i 
the contact screw, the tension of the armature apt 
the distance separating- the magnet cores from the a,^ 
A typical vibrating bell of the so-called irou -boxj 
depicted in Fig. 2, while at Fig, 3 is shown a c'omph 
trie bell outfit, including belt, push-button, battery, » 
staples for securing it in place. This outfit forms jn'jij 
cient front door bell set, or in any other applical' 
tancea not exceeding fifty feet. In Fig. 4, are i 
few ornamental brass push buttons. 

It is not always desirable that the electric^ 
that of the somewhat noisy bell, and for this clasB,q 
' ' n instrument known as a busa^ 

notbii)g else but a neati i 
cliacLism, without any gong o 
so thai the armature in it ca 
rapidly, sending out a l"ud bui_ , 
similar tf) that of a hee It M-p . .. 
ployed in offices or other qwe^ j 
where the bell is toi naisy or |— ^ 
it is used in conjunction with a," 
either the buzier or the bell ^ 
indicate- one or the other 
signals. For instance ._ 
houses, the bell ind buzzer aij 
side by side m the k tcl en ant, 
nei-ted to tivo push buttjis that tlf 
indicates someone at the front doL 
the Buzzer a call from tl e dining r 
table, etc. Somet raes a number of 1 
with different toned gonfi are arrangei.— 
a set, the meaningpf each being quite dist net Common loa 
of the odd gongs are; the cow bell the cocoa wy>d the slq 
bell; the split gong-; the chime gong etc A neat and i 
made buzzer is seen at Fig. 5. 

_A recent innovation m the realm of electr c signallS 
devices is the electro whislle. This instrument gives oiit j 
more or less shrill whistling note qu te d st net from at 
other device, It is built on the sarat pr nc pie as the vib» 
ing bell, excepting that the armat re of the bell s subst tufl 




Flfc'. 3. 



w 




diaphragm, a 



} 

^B by .an iron roil anil a thm 

^H whenever current is siippt 

^1 Ter. 1, and Ter. 2, its path is around through 

^■r ing coil, and closed contacts, A, At this iunc 

^H the magnelizing.coi\ has drawn iorwatd ttvevti 

^H sboivn, and this also moves the diaipHragm, U 

^■is attached. The movement oi the ro^ and 



'#^ 



)wn at ^igjS 
binding poM 
the magn^HL 

ture, howeva 

1 ■™\\\t'\\ \Vt » 
4\sc, s\«iiA^ 



Isly' breaks the contact boiween the springs, A, and tlie rod 
■ 1 irs parts rtiurn to (heir original position. In practice, 
1 allraction and release of the irgn rod and also the dia- 
phragm occurs at a \ery high rate, resulting in a whistlini! 
sound being emitted by the diaphragm. This sound may be 
I gr caiiy acnplified and directed ty attaching a brass or other 
' il horn to the front of the instrument. This arrangement 
i very satisfactory service as a telephone call in power 
"s or other noisy locations. 

,_e apparatUiS so far mentioned, 'form the usual comple- 
rOE audible electric signalling devices, but before taking 
up the study of circuits and other details, 
reference will be made to a very important 
instrument, variously called an indicator or 
aniiundaior. A cut of a 6 position annun- 
ciator, or ore capable of indicating 6 dis- 
tinct cails. individually, is portrayed at 
Fig. 7. The annunciator is a very wt- 
tensively used instrument, particularly in 
hotels, and other places, where a great 
of different calls are to be registered at one central 
pcdnt, such as a hotel ofEce. 

Tts principle 
actu.il is ba 
ii;.i.iT the electro- 



uon with th, 
previously. 
most cases a 
or buzser is 

ranged to opei 




TCRM.Z 

I'ut \i". :innunciator ""*■'' 

iistlf cJiiits no ap- 
preciable sound at all. Each shutter or drop, bearing any desired 
number, name or letter, is normally held out of sight, in the type 
shown in the cut. When an electric current is sent -frftm a oertam 
corresponding push button, however, the shutter is instantly re- 
leased by an electro-magnet, and drops down into sight In the 
cut, Nos. I, 3 and 5, have been re- 
leased by the electro-magnets oper- 
ating them. The shutters are reset, 
toawait another call, by pushing up 
oil a button at the bottom of the 
cabinet, after each indication. In 
some annunciators this resetting 
of tJie shutters or indicating need- 
les, is accomplished automatically 
by each succeeding call. This is 

> good and a bad feature, 

i the second call may 

vrMetting all previous calls, 

e'-fliey have been seen or an- 

, Hence the manually reset 

i generally the most desir- 
. — A sketch of the working action of a 
is shown schematically at Fig, 8. 

An elect ro-rnagnet is arranged with a pivoted soft iro 
', to which is attached a trip bar, so that when Ih 
._ _s energized by passing a current through it. the a; 
e wilt be attracted, raising the Uvp 'oit ot fewsE;^. ■^'^^ \ 
shutter or drop, ■which tests oti a. ^Snq'i. A».ag 
itter is reset out of range oi the VvnAovj m xVe c 
hing upward on a buuon a 





ne^S 



. .. fall over 
eJge of the shulUr, ' 
reiaining it in place, 

©til another call occ 
There are many diffcn 
styles and makes ol i 
nanciaiors upon the market, but they all operate fcy meaoa of 
electro-magnet and armaiure of some form. 
THE WIRING. 
For ordinary electric bell installations it is usual to a 
ploy copper wire, about No. 18 gauge, B. & S. (BfowoaJ 
Sbarpe), with two coatings or wraps of waxed cotton oycj 
for insulation. The number of feet per pound of office a 
annimciaior wire, used for bell work, etc., is as follows: 

Office wire; 
No. B. & S. gauge. Feet per ' 

No. 12 3S 

No. 14 55 

No. 16 95' 1 

No. 18 13S . 

Wir. 



The annunciator wire, or common bell wii 
layers of cotton merely wrapped around the 
which is then soaked with paraffine wax. It is e 
elled. 



ail/ linn 



Office wire has two cotton layers braided, which i» t 
so easily unravelled and consequently more preferable. T 
inner braiding is filled with a moisture repellant compoin 

The cheapest wire to buy. of course, would be No. i 
gauge, as it contains the greatest number of feet to the pom 
but (t is only suitable for comparatively short lines, as it i 
too much resistance for the low voltages irtiUzed in t 
work.. No. 18 is permissible for bell or annunciator circu 
up to a distance of 100 feet one way or 200 feet of wire in t 
circuit. For circuits of 100 feet -to 150 feet one way. use N 
16 gauge wire. Circuits from 150 feet to 200 feet, No. 
wire, and circuits of 200 to 250 feet one way, use No. 12 wi 
For circuits of greater length than these it is not practical 
ring the bells direct, as they require too much 
amperes, which necessitate a very large battery to corop^ 
sate for the volts drop in the line or circuit, and also fir 
copper wire. For long bell circuits, the most practical 1 
rangement is that involving the use of a high resistas 
relay, which is actuated directly by the push button and b) 
lery, over the long line; and the relay then closes a lo( 
circuit containing several feet of wire, a battery of a f< 
cells, and the bell. The relay is wound to a higher resis-tan 
than the bell, and does not require nearly as mudh current 
amperes, so that smaller line wire may be used. Relays 9 
quite sensitive, and are the same as used on telegraph linu 
the resistance varying from 20 to 100 ohms or more, depen 

Iing upon the length of the line. A long distance bell c" 
I with relay_ is shown at Fig. 9. 
In this arrangement, whenever the push button i. 
pressed, current from the battery is seat over the line whii 
' actuates the relay electro-magnets at the other end. Tl 
magnets then pull forward the iron armature shown, closii 
the contacts of the local circuit, and allowing the bell to ri! 
from its local battery. A spiral spring \io\&% t\ie relay arm 
, ture normally away from the magnel po\e& ai\4 toa'a 
»cre\y, leaving the local bell circuit open. 




Ill general to ring s 
May required cither 
[. dry cells or wet 
^8 ^1-ammoniac-car- 
jW-ztnc), is about 2 
tals for circuits iiii to 
^ f«et, one way; cir- 
"■ up tt> 75 feet 3 
»* 100 feet 4 cells, 
[The number of cells 
tied will depend 
i the sUe of the bell to be operated and the length of the 
i;dt The standard siies of bell gongs vary from 2 inches Up 
|12 inches, the latter requiring about 8 dry cells to operate on a 
" lat not exceeding ?S feet in length one way. 

the past few years there has been a new source of 
: for bell circuits introduced, that employing a small 
tep-down transformer, excited from the A. C. electric lighl- 
Qng mains, in the house or building. The transformer does 
"fat take a current worth mentioning, and supplies a reliable 
jource of power for bell circuits and the like. A circuit 
^agram for it is shown at Fig. 10. The secondary coil has 
%reral taps brought out from different turns thereon, ao 
'(at various voltages may be applied to the bell circuit, gen- 
tally from 6 to 24 volts, A. C. (Alternating Current), 
r A few words will now be devoted to the subject of bell 
M^tff in general. Some of the basic prindples underlying 
£od bell work, arc: that all wires must be carefully run and 



=iiiy«tt.ES5i 




^1 Insulated from contact with gas, steam, or water pipes, 
i all joints in the wire circuit should be soldered and taped 
k with black friction ^a^pe. The best practice in running 
lore cotton covered bell wires, is to either have all 

J bunched into a cable, and the cable secured in 

! by fibre or leather straps, or to run each wire separate 
I its neighbor and securing each in place by means of 
staples. Insulated staples, such as the Blake, are best, 
■d sometimes the two wires of a circuit are held under one 
pulated staple, there not being much chance o£ short-cir- 
Uting the two wires together. Unless continual trouble is 
' ', therefore, the individual _____ 

trill be well insulated by 
J into a cable, or by keep- 
_. ; separate. A good 

ale form for several pairs of 
ires, results by wrapping the 
Tlole cable with insulating fric- t 

n tape. This is often employed ' 

r interior telephone work and ^ 
1 proven very satisfactory. 

*" I new bell work where the building is unfinished, tlie 
i are readily placed in the walls and floors, making a 
Ely concealed job. Where the bells have to be installed in 
Bjd buildings, the wires may be run inside of the walls to a 

treat extent, by fishing them from hole to hole, making small 
oles at the baseboard and at the ceiling. Also by taking up 
L short piece of floor on opposite sides of a room, a steel 
^h wire or snake, as it is often called in the electrical trade, 
-easily pushed along between the floor beams. _ When the 
Bh wire appears at the opposite hole, the bell wires are at- 
'-*— ' 'o It and pulled through to t'nc ovVvw ^^'At. ^'^™'^; 
makes a good appearance, 9a.Tticu.\MVj « «**! 
i moulding is used to matc\i Ac Vt\m c.\ 'Cat xqctr 
mich h is Jnstalied. 




"•TFirtt class liel! installations have the wires placed in 
pipe the snme as rrgular elcclric liglit wires. 

Before goioK into Ihc varimw systems and cooaecbi 
which may be used fur electric liclls and aiinanciator- 
will be well to give a few simple iastruciiwns — "'— " 
out of bell wires, batteries, eic. 

The ^iiiiplesl niclhoc) by which to test oul any wires 
(heir continuity, hut not always applica.ble, is that known 



n. 



in ii^H 

ecb'O^I 

res (^1 

own H> T 



i 



Fig. 13. 
the ground test. The manner of accomplishing this Wst 
depicted in Fig. 11. where G is an artificial ground at i^ 
connection, through water, gas, or steam pipes in a bU 
ing; B the testing battery of a few dry cells: T the ((at^^ 
bell buiier, or sometimes a telephone receiver for It 
lines having high resistance, and L the wire to be Maj 

The diagram given explains itself, the only thing ntx 
sary to do, being to connect the ground wire C to viy n 
desired, and then testing the ends of the wires at A, HI 
the bell rings, when the wire under test is consei{iMB 
known to be continuous, and also 
3 certain wire in the system, 
which it is well to call No. 1, 
The wires, if more than two in p, jg^ 

number, should always be tagged 

.and numbered, after which it becomes a simple niailex toi^ib 
hiTok up the wires to any form of system desired. 

The ground lest, as previously mentioned, is not ao) 
times applicable, due to the absence of a handy ground i 
nection. In this event, a somewhat different procediiH 
pursued with the same results, that is, the testing ,(' 
individual wires of the system for continuity and nuial] 

The common circuit arrangement for this full metallid't 
is shuwn at Fig. 12. First the testing battery is cotiaei 
across any two wires as seen, and the tester at B tri^< 
ferent wires or cable terminals, until his bell or relay ,' 
bell for long lines, rings. He then knows that he haA 
first two wires continuous, and usually they are taggM 
both ends Nos, 1 and 2. By joimng both line terminals, l>i 
2, to one pole of the battery at A, and the other batttiy «' 
to a third wire; the tester at B, by connecting his one 1 

^ ris.i* U ns.B ' 
terminal to lines 1 and 2 and testing the various cable CD 
readily finds one that rings his bell, and that one is Ho, 
line wire. This is followed out until all the wires iho« 
and 2 in number are ascertained. At this stage of the ' 
however, the wires 1 and 2 are not known one from uia 
but by separating their respective ends, aw4 tovi\\c«.m« < 
battery pole to No, 3 cable wire, and v\\c o\.\\m vw* 
either No. I or 2 at the terminus A, v\ien -jjii^i 




jystem allowing either push button to operate the oopoflU 
bell, over two wires, but two batleiies are required, In m 
gram 19, the standard return call bell circuit is seen, t 
ing but one battery and three wires. 

A common form of four drop annuticialor or ladicaiot'^ 
diagrammed at Fig. 20. 

Whenever Che push. P 1, is pushed, for u]stai>ce, it (_. 
the arcuit around through the annunciator trip magnet t 
' ; call bell in scries with the circuit. 

A more elaborate iad 

at Fig. 21. This haa p 
turn call LeIU St etj 
party's push button lb 
tion, so that the centr 
operator at the indiciti 
A. N. may push the pa 
responding buttoti fi 
any call rung up, iJu 
signalling the eaUl 
party that his call ft 

A few diagrams' i 
appended here for tl 
trie gas ignilian syslems. The common pull chain igniter bUT 
is given in diagram by Fig, 22; where only one wire leads fi 
the gas lighting coil to Ilie burner. Common ground conoei 
tion is effected in the basement to the gas pipe, 




■through the gas fixture. 
The a«io 




IfiiifTsW. 



burner and 
cnnneciium are 
illustrated a t 
Pig. 23. At A, 
arc the connec- 
tions for a sin- 
gle push button 
control of the 
burner, while at 
B, is a double 
control of the 
burner, such as 
having the 
pushea at oppo- 
site sides of the 
room. Fig. 2A. 
is another cut 
of en auto- 
matic gas burn- 
er hook-up. 

The high 
tension gas ig- 

much used in theatres, as auriliaiy. in case the electric light 
fail, is seen in diagram Fig. 25. This system employs either 
jump spark coil or a special frictional generator which develop 
about 50,000 volts, at a turn - 
the handle. The burners are la. 
with fixed spark gaps, and a ni 
ber of the burners are connec 
in series. The air gap, which th« 
spark has to jump on each bumei 
is about one-thirty-second of at 
inch, and therefore there arc ap- 
proximately thirty-two burners t( 
every inc^^|^d[ available fron 
the chai]BPVHtlU' '" Ptac 



^ 



FI&.21 




n for a 



:ombmatio 



S 






I 



t [tiJrf E. 



■ioened the 
t will ring. 

the day, if desired. 
'( circuit syiU 



ilie battery drcuit. so li 
dtagramined i 





.1^ ttattcry is always closed through 
! mndow springs and relay magnet ,•«« 
bi. J If the springs shoald be opened 
tUBing the window, the relay mag- 
S IVOUld have no power, and releas- 
th« acnature, would cause the alarm 
to ring. See complete details of 
rglar Alarms in Lesson No. 9. 



'aC^ 



© """V- 



LESSON No. 2. 
PRIMARY BATTERIES AND DRY CELLS, 

rHERE are various kinds of battery cells used in practical 
deetrical work, the two principal classes being; the 
primary ceil, and the storage cell. The former or pri- 
mary cell wd! be treated upon in the following para- 
iSlM, the storage cell receiving exhaustive treatment in a later 
jptcr, devoted espedally to it. 

The discoverer of the primary cell was Alessandro Volta, 
■*f the greatest scientists of the early electrical experiraent- 
and the greatest opponent of Galvani, bovtv on ^t^ix'iM'j 'ft, 
), at Como, Italy. 



J^'?I*'?lTa buy he ; 



/try mt 
771 lie 



tilic and electrical 
ptra through w" " ' 
made himself 

Voiia was 3i 
ordinarily devci 
m enter, and due to t 
is not only the first e 
.._ . trie battery, but he ) 

invented the well-k" 
electrophorus, also the electric condenser is his inveiiti( 

In the year 1800 he sent a description of the "Voha 1_ 
to the'Royal Institute of London, and in the year I80I he % 
called to Paris by Bonaparte. Here he demonstrated hia c ' 
ments to the Academy of Scientists, in the presence of Has.. 
In the year 1804 he ceased teaching-, but in the year ] 
accepted the nomination as director of the philosophical fSCL 
of the University of Padua, which was tendered to himlj 
Emperor Francis. 

His last years were spent in his home town, Couo, and I 
died there at the age of 81, on March 6, 1826. 

Prinuiry cells include all those forms which produce ai . 
trie current by voltaic or galvanic action. Each cell is made I 
of two dissimilar elements, termed the z'ollaic covfle, which u 
in turn immersed in a saline or aciduated solution, kno^ 
technically as t^iceJcctrolyie. 

The elements are selected for a cell, 
so that one, termed the anode, or pos- 
itive element, will be acted upon by 
the solution or electrolyte, more readily 
than the cathode, or negative element. 
The anode comprises that clement at 
which the current enters the electrolyte, 
and the cathode or negative element, 
that at which the current leaves the 
electrolyte. 

The chemical action occurring in tlit' 
production o£ electrical energy is as 1^1- 
lows; The anode Is slowly consumed 
by ojqfgen from the electrolyte, and hy- 
drogen gas liberated from the electro- 
lyte or solution lends to gather on the 
face of the cathode. Hydrogen gas is 
a non conductor, practically, and hence a thin layer 
on the cathode element hinders the passage of i 
rent, resulting in what is called polariitation. Some nil 
reduce or abolish this polarization | 
which occurs, is always resorted 
primary cells. A depolarizer is a sn . 
that will readily combine with the free!l( 
drogen gas, and is placed close 
ihode or negative element to remove 
gas formations at this point. Solid 
!i(]uid depolarizing agents are comm 
employed. The solid depolarizer material 
are arranged sometimes about the ea " 
in a porous cup, through which the . 
trolyte can seep. When in liquid forijj 
the depolarizer is sometimes placed -ii 
I porous cup around the cathode, or it 
P be of a different specific gravity than 
electrolyte, allowing one liquid to 
main above the other due to their va 
ing densities. The depolarizing liq 
vrth the electrolyte v\ some ce\\&. 
t necessary to describe here aU o^ ttvc N3.no\\!, v 



Fig. a 




^^ H4i«^-M 

: ary tells that are and ■have been used, but onI^»£2£l 
^ ... )irincipally employed to-day for bell and signal wo^,~-, 
-I, i''iiij jiTijll lamps, mctors, etc. 

'Ihe chief dilterences in tlie use of primary cells depends 
upon whether they are to be used on closed drcttit or continuous 
duty, or for ofen circuit or intermittent duty. Open circuit bat- 
teries are utilized whete electric current in small quantities is 
r,-.;ii'i,'i intermittemly, as in the ringing of bells, gas-lightiae. 
[■■'.'; ■■ iurs, etc. The closed circuit battery is employed when a 
. iirrent is reiiuired steadily for long periods of time, as in 

I .1 rijal telegraphy, fire alarms, etc. The gravity or Daniell 

i-cll ts inucii used for closed circuit work, as are also the Gordon 

For open circuit requirements, Leclanche cells and dry 

used very extensively. 



Ci:lls. 
cells . 

The standard closed circuit 




leaves and the jar filled wi 
In the chemical action o 
copjier plate, and sulphate o. 
To increase or quicken the 
pbatc is s>>metimes added U 
r^t-t Lip, If the 



;I! for telegraph work in the 
United States is the 
Gravity, Crow -too I or 
Daniell cell, as it is 
variously called. Tht 
gravity cell, Fig. 1, con- 
tains a. zinc block Z, 
suspended from the side 
of the jar. while a num- 
ber of copper leaves C 
stand on edge at the 
bottom. A quantity of 
blue vitriol (blue-stone 
or sulphate of copper) is 
poured over the copper 



this cell, copper is deposited on the 
zinc is formed at the zinc element, 
ciion, a small quantity of zinc Sirf- 
the solution when the cell is first 
worked enough, all the solu- 




II become blue and the zinc will blacken. It the 

•ery dirty from this cause, it should be removed, 
' washed thoroughly. All the electrolyte or solu- 
'so be thrown out, and replaced by new sulphate, 
inserted, and then the copper and zinc elements 
logether for a few hours when the cell is ready 
duty. Its voltage is 1.1 volt, and the current ap- 
lOne-balf ampere. Warmth causes it to produce a 
;£nt, and it should never be allowed to freeze, 
cell must be used only where it can' be leept con- 
im circuit, and not left standing idle for any length 
,._^ The temperature of the cell should be kept above 70 
:«CS Fahrenheit for best re- 
the resistance of it in- 
ises very fast with a decrease 
temperature. The internal rc- 
tance of the cell is from 2 to 3 
ohms. A blue color in the bot- 
tom fi the cell denotes a good 
condition, but a brown color 
shows that the zinc is deteriorat- 
ing The bliie line which mltlcs 
the boundary between the copper 
sulphate and the zinc sulphate, 
should stand ahout half-way be- 
tween the electrodes. If it comes 
loo close to the zinc, some of 
[he cnppcr sulphate can be drawn I 
■-"1 ^y siphoning, or the cell 
■ short-circuited, thus pro- 
... more zinc sulphate. If the t 

_ J :..\ of water and cop per- crystals 

^^^jii J .pounds of-crystals to make a 

!■■[_ -'^ 




.■,« !fJP» 



Itx oi (he !)«■( lypei of dosed circuit cell designed t 
ially for continuous duly and fairly heavy curKnts, with 
capacity ii ampere hours ranging from 100 lo 600. is the Gor< 
frintary cell. A view of this type of cell is shown at Fig 
This type of cell is a triumph of the laboratory, and is at o 
suitable either for open or closed circuit requirements, with V 
little deterioration on open circuit. The mechanical consti 
lion of the cell is especially good. The copper oxide (or ne 
live element) is used in ^ake form compressed in perfora 
metaJ cylinders (see Fig. No. 3), the perforations of which 
closed in such A way as to prevent leakage. Attached to 
cylinders are three porcelain insulating supports (Lugs); t 
these lugs the zinc (or positive element) rests, thus preven 
it from coming in contact with the copper and forming a i^ 
circuit within Ihe cell. 

The zinc is made in circular form and is held in place 
the lugs— it does not hang from ifte cover of the cell. A faea 
insulated connection wire is firmly attached to the zinc. 

The electrolyte is a strong solution of caustic soda. 1 
top of the solution is covered with a heavy mineral wl tuch J 
paraffine to prevent the soda solution or electrolyte from e 
orating. 

The cells are usually supplied with porcelain or glass ]1 
and the proper amount c ' 

chemicals for a charge are CABBOM 

put up in scaled packages. CRrSTALS,^ ■ ^ 

This form of primary cell 
has an initial E. M. F. or 
voltage of .95 volt, which 
drops to .70 volt when the 
external circuit is closed 
and the load put on. The 
internal resistance is ex- 
ceedingly low, varying from 
.02 to .089 ohm, accord- 
ing to the type and size 
of cell. The following 
data shows the performance 
of these batteries : 

Continuous rapacity in amperes 1.5 2.5 4.0 6,0 7A M 

Maximum capacity in amperes 7.49 9.53 15.51 26.68 33 Ji.M 

Capacity in ampere hours 100 150 300 400 

Interna! resistance ohms .089 .070 .043 ,025 

This cell is well adapted to small lighting plants, gas if 
tion, operation of spark coils, etc. 

For the operation of spark coils, small lights, etc., use 
often made of Bunsen ar Grenet batteries. These cells sup 
a continuous current until they are exhausted, when they 
recharged. 

The Bunsen cell consists of amalgamated zinc and carl 
elements, the latter immersed in dilute sulphuric acid, 
with fuming nitri 
as a depolarizer. 
Bunsen battery is 
Improvement i 
Grove cell, ii 
platinum was used 
stead of carbon, 
voltage or e!ectro-r 
live- force (E.M.F.) 
1.89 volts. The carl 
electrode and the nil 
acid depolarizer 
placed in a porous c 




flS.6 




being seen at Fig. 

^ Meylan, in 1386, made some elaborate tests on the Bunsen c 

"]i (fte fothwing results: 



_Tbe cxciling Jiquid or electrolyte was sulphuric acid, con- 
. iiag of equal volumes of 60° Batime, sulphuric acid and water. 
Ble depolariier was nitric acid of 36° Baume, specific gravity. 
"ic electrode having an active surface of 116.25 square inches, 
.ternal resistance 1.27 ohms. Internal resistance 0.04 ohm, 
Ding to 0.035 ohm, and rising to 0.12 ohm. 

artii^ 1.9J volts 

" ' ;s closed cir- 

1.87 " 1.42 amperes 8 

Kfter 24 hours closed circuit 1,77 " 1.33 " SSwatihrs. 

Mter 30 hours closed circuit 1,73 ■' 1.24 " 70 " 

■ Tile Bunsen and Grove cells have the advantage ihat no salts 
t tiaed in their solution, so there is consequently no troable 
-Om cryBtallization in the carbon or platinum compartment. The 
solution, however, of nitrous fumes which corrode the battery 
imectiona and demand special ventilation arrangements i 
d feature. 

A battery which has been extensively employed abroad for 
qieriinental and laboratory purposes is the paiasnum bichro- 
\ate or Grenel cell. Its usual form is shown in cut, Fig, 5. A 
niTrcell bichromate battery is shown at Fig. 13. It is eom- 
Msed of carbon and zinc electrodes immersed in an electrolyte 
^ lOO parts potassium bichromate, 100 parts of water, and 50 
^rts of sulphuric acid. When not in use the zinc element is 
"fltdrawn from the solution to prevent local action and ex' 
ustion «f the cell. 

For open circuit requirements such as the ringing of bells, 

jnskUing devices, ignition spark coils, and the like, or where 

maU quantities of electric current are used intermittently, the 

ninm Moride cell is generally utilized, as it has many 

_ mdable features. Ammonium chloride forms what is called 

monly sal-ammoniac or chemically NH,C1. Sulphuric acid 

E expressed chemically as HiSOi. In ammonium chloride cells 

" ' ' *s necessary, unless the carbon surface exposed t 

n is extremely large compared to that of the lini 

One of the earliest and best cells of this type was that 

■olved by Lectancbe, in 1868, and it is named after him tlie 

^etdttrhl cell. There are two general forms of it in use; tl 

reus cup cell, and the agglomerate block cell. 

In the porous cup type, seen at fig. 6, the zinc element, i 

! form of a rod, is placed in the outer vessel, containing a 

monium^ chloride (sal-ammoniac). The carbon 

X a porous jar, which is filled with a mixture of pulverized 

on and black oxide of manganese, preferably in needle- 

h -or crystalline. The porous cup must be of good quality 

I ijuite porous. The E. M. F. of this cell is 1.48 volts. The 

jrona cup does not usually last longer than two years. One 

Brt of zinc dissolved should reduce two parts of manganese 

Kaxide, and should in turn exhaust one part of ammonium 

ploride. Strong ammonium chloride !.■; preferable as it is a 

itUr solvent for the zinc oxychlorides formed. In figs. 7 and 

■JUe shown, respectively, the porous 

' » and agglomerate block Leclanche 

Tte agglomerate block type of 
BSlruction, takes its name from the 
■t that no porous cup is employed, 
: tfie depolarizer is made in two 
xs, which are held against the car- 
H plate or electrode by rubber bands. 
m cakta consist of 40 parts bioxide 
I toanganese, 52 parts of carbon, 5 
I of gum-lac, and 3 parts of po- 
um bi sulphate. These are com- 
_ or bricquetted at a pressure 
300 atmospheres at the temper- 
o£ boiling water. Ammonium 
™( of the best quality must be «se4 iot V;W, ^cwto, ^* 
U 




FIG. 9 



commercial sal -ammoniac is liable to contain InpifJI 
wbicb tend lo increase the ruisUnce of the cell. 

Tbe common form of Lccbnche cell uscU in tUis cftui^i;^, 
bell WDtk, emjilDys a saiurAtciJ solution of gaUammoniac;. K 
a line rod about }i inch In diameter for the positive di " 
or nesative terminal pole, and a large carlxin cylinder a 
Inches in liiamcicr for the negative electrode or positive I 
mlnal pole. The electrolyte is made by ilioroughly diasolf 
about Ji pound of sal-ammoniac in the jar a little m6re fl 
halt filled with water. N'o depolarizer is used, the cotuaden 
STtater area of the carbon electrode, as compared to thW 
the zinc, being considered able to care for the prodticUoo 
hydrogen gas. This cell is veiy poor, however, if much li 
is placed across its terminals, the carbon clement becon 
covered with hydrogen gas bubbles. DaWu'; the carbon Jsi 
oven often gives increased results in the action of the batti 
The internal resistance of the Lcclanche cell of tho | 
cup type is approximately 1.5 ohms. 

The Fuller battery cell is one that has been much uSed 
telegraphic purposes in England, and' 
experimental work in this coiuj{ry. . 

< I ■* often called the Mcrcury-Sidifim 

^"^^j battery, owing lo these eleiyntl bc 
" t-J the chief constituents in its t«)f!S' 
rn » @ Fig. 9 is a cut of the Fuller cdt- 

comprises a gbss or porcclaip otmtl 
ing jar, inside of which is. fitted a jioi 
cup, containing ,a .pyramid shaped zine electrode, 
tticrscd in mercury at the bottom. The mercury thus k 
the zinc continuously amalgamated. A carbon electrode 
placed in the outer vessel, which receives the depolarijlng I 
lution. The acid electrolyte for the cell is placed in the pqni 
cup, The electrolyte is mixed by adding 6 ounces of poli^a^ 
bichromate and 17 ounces of sulphuric acid to 56 o«nc«i 
soft water. This is poured into the glass j'ar. In the ( 
cup is placed two teaspoonfuls of salt; one teaspoooiul 
mercury, and the cup filled to within two inches of the top v 
soft water, with the zinc electrode in place. 

The color of the solution is orange when the celt ! 
working order, and the internal resistance varies from 0^ 
4 ohms. The Fuller celi can be left oa open circuit for Kvj 
months at a time, without any appr?ciable deterioration. 
E. M. F. is 2.14 volts. 

Through the whole category of batteries, there is one « 
has probably reached a greater adoption than any other,- . 
commonly called dry battery. The dry celi lias been a boon U 
user of pocket flash lights and other portable requireme 
The voltage is about 1,5 vlts and the current from !■ to 
amperes for short intervals, depending upon the size of 
cell. They last several months for flash light work, and a 
a year for bells, etc. The cell is generally discarded for a 
one, when exhausted, altliough they may be recharged as '• 

Procure a machine drill of about l,i" to 3/16" 
and drill holes carefully till the drill loudies the carbon. ■ 
not be afraid to drill through the entire portion of the 
polarizer, as it is necessary that it gets air and electrolyte, 
is obvious that drilled holes do not throw up a rim, but I 
a flat, clean hole, making short circuit entirely out of theq 
tion. We would recommend to drill about 8 or 10 such ho 
being careful to see that all manganese (black filler) is carri 
'~' of tbe hole. Blowing hard in t\i« TsoVe w\\ Msw'iWj si 
15 



•»5 




rieetiy. We also recnmraend, lo drill each 
. rapidly as possible, because the drill itself, 
I contact with both linc and depolariier 
the act of drilling, for the time short- 
:uits tile cell. 

Next prepare a solution of 10 parts (by 
iffht) water and 5 parts of chloride of zinc, 
iidl can be bought for about 50 to 60 cent? 
I "pound. Ten cents' worth will do for about 
^en- dry cells. If the solution is kept in a 
W'«toppered bottle it can be used over and 
K as each cell does not absorb much liquid. 
rtht solution must be well heated before used, 
■ihonld not boil. Insert the cell in this liquid 
T.leave in same for about 20 to 30 mintnes. 
VecHs should then be taken out and rolled on 
ifldor. Each hole should now be inspected to 
Kfjr if it is clean and if no tiller touches ili 
[.Now dry the cell carefully, and if possible 
i hole a dry wooden plug, which can be cut 



"Ke battery is now ready for use and in most cases will 
'"■■ from 8 to 12 amperes and about 1.3 volts. 

rnetliof! of testing dry" battery cells, etc., is slv>wn by 

diagram, Fig. 14, where B is the battery and H the volt or 
ammeter. Dry cells of the 
Standard size, vh., Z'/i'xS'. 
usually register l.E volts per 
A cell indicating the stroogest 
circuit by an ammeter, the read- 
ing varies from 15 to 25, ac- 
Q cording to the type of ceil. The 
cell indicating the strongest 
amperage is not always the 
noBt satisfactory one for dura- 
tion or life. Some of the best 
dry cells register but 18 am- 
peres when new, while some 
t will show 30 to 35 amperes orl 
sliort circuit through the am- 
meter. It is to be deplored 
that the cell test by the short 
> circuit through an ammeter is 
employed so widely, as it is 
The correct method is by 



'^ (| ^ 



CELLS IN StRKS-MULTlPLt { 






Ihfr worst possible thing to 
iBMns of a good voltmeter. 

. The outer containing jar of a dry cell is of zinc i 
llpes, The carbon or negative electrode is suspended 
^Ire of the zinc container, and forms Ihe positive terminal 
mt of the battery. The car- 
^ element must not touch the 
|A«, The zinc chamber is pro- 
'tted inside by several layers 
t Wotting paper, and filled 
—^ ift a mixture consistmg of 
Miriered carbon, manganese 
iBKctide and sawdust (or some 
JJji C t absorbent substance) , 
jfilt mixture is saturated iv-ith 
I »d«tion of sal-ammor.iac. 

ftAer the cell has been thus 

Wl up, it is sealed with seal- 

tawax, and the whole slipped 
nto a carton or pasteboard 





.ycacA. aV *■; 



cylinder of carbon powder and manganete dioKidc. The fit 
mixture composition is *inc oxide, ammonium chloride, l_ 
zinc chloride, 1 part etch: plaster o{ Paris, 3 pails; watSf 
parts. The tntemal resistance is about 0.3 ohm, A cut a 
modern dry cell is seen at Fig. 10. 

The arniMSfmeitt of the various cells of a, battery, w. 
more than one cell is used is important, and depends upon 
class of work it is to be used upon. In connecting up a nun 
of cells in series to attain increased voltage, the carbon dectn 
or pOsitiYC pole of one cell is connected to the zinc e]ectr 
or negative pole of the next cell, etc., as shown in Fig. li 
With this arrangement, the voltage across the line wires COB 
from the battery is equal to the number of cells times the volt 
of WW cell. Hence, if one cell delivered 1.5 volts, then 3 t 
would deliver 3 times l.S volts, or 4.5 volts. The measurai 
of the voltage or current of batteries is readily made 1^ the 
of a pocket volt or ammeter, a cut of one appearing in Pig,' 

When more current is desired than that obtainable Iron 
single cell, they are arranged in multiple or on parallel, ai 
Fig. 11 B. If one cell can supply Vi ampere normally, '"^ 
three on multiple could supply three times 'A ampere, or 
amperes, but at the voltage of I cell or 1,5 volts. Here all 
carbon poles are connected to the same line, and all the i 
poles to the other line. ■ 

A combination of the above two conditions, is illustrAed 
the diagram Fig. U C. This allows the battery to care for 
desired voltage and current in amperes. The voltaee develo 
by the battery is determined by the number of cells cofuec 







volts. 'J 

would be three times that per cell, or IJ'j omperes, not t) 
times 1 ampere, because the cells are in series and have ti 
the resistance of one cell. To get 3 amperes ai 
the basis taken above, it would be necessary to connect 6 
of two cells each, across the lines, instead of 3 files. 
PRIMARY BATTERY CELLS, 

Eleclrolytf CaHio-Ie Dcpoliriicr E.M.F. Volb Stn 

iolulifin of NH.Cl i 





Danidl Zinc sulphate 
(ciowfow) 
LKlancbe Solution of NH.Cl Ci 

Stic PgUsb. 



r words regarding fiashUghts and their barieriu m»y 
InHrKJf, as Ihey are often misunderatood. Al Fig, 15 




instruction, ] 

-JHied read- 

E^e sketch Fig. 16. A, B, 
__i .push button to open and clfis 
^usually tungsten li lament, as it is 




^CARaeOARD COVER' 



C, the battery circuit 
; the circuit at P. the 

Zy^ to 3 times as effi- 
cient as the old 
carbon Rlsment 
type), being placed 
at L. Flash-light 
batteries give from 
Z to 3 months' 
service if used 
only a few limes 
each day. " 
burned continui .._ 
ly, Ihey will light 
the lamp tor from 
2 to 3 hours. 

A new form of 
spring binding- 
post, which has 
received wide rec- 
ognition, wherever 
batteries are used 
is illustrated by 
cut Fig. 17. It IS 
reasonable in first 
cost, and easily ap- 
plied by a machine 
, by simply pressing 




FiR. 17 



Fig, ISA- 



IS 



jwdde. The f 
iuin chloride, 

A cut a 



STORAGE BATTERIES. 

. ^^ TORAGE hatlfries differ from primary baltcries, In ^ 
^^ tliey can be diargcd and recharged by passing an tf 
(,^J trie current through lliem. Storage battery, i 
battery and accumulator arc the variuus terms 
raon use to signify an electrical device in which dicmicaj ac^ 
is first set up by the passage of an electric current, after « 
the device is capable of giving off electric current by tnd 
of secondary reversed chemical action. Thus any form oi,9 
taic couple that is directly reversible in its act" 

a storage battery, 
tion of storing 'c 
energy in the battery tt 
passage of a current 1 
an external source, fi 
as charging the 
When the baitefy ia-jL 
off current, it is sai4^ 
discharging. 

\ storage battayp 
two elements, or ptatra^ 
Klectroilcs, one posi^VH 
one negative, immcrs 
an electrolyte of addSj 
water or some OthrCT J 
tion. The positive aarfS 
tive plates 
composed of the s 
terial, but sometiine»_^ 
are made of two C" 
materials. At Fig. 
e grid before the active material has been li 
in it. The various methods of forming the grids and i) 
the active mixture is shown by Fig. IB. 

The action of a storage battery is as follows; — The5 
duclion of current by the battery after charging, oxidi«l( 
may dissolve the material of one plate, and the eleetii."^^ 
exhausted in the process. The hydrogen gas liberated*^ 
the inactive' plate, and finds there a depolarizer. This i 
ually decomposed and reduced as it supplies oxygen toS 
hydrogen, and after a time the battery is exhausted, 
being capable of producing a current 

To recharge or regenerate it, a current of electricity , off 
posite polarity or direction to that which the battery iotB 
produced, is passed through it. By tliis raear 
chemical action is created, which reproduces by elerti 
reduction the previously attacked e\ec\iode on istlc i ' 
I simultaneoasly forms upon the otVier p\ate \\\e dc^oW 




rig. la 



shown s 




Pk^ilyjia, DnriDg liie course of these two actions, the 
electrolyte solution is restored 
to its original slrensth. When 
the charging has prugreased 
sufficiently long, the battery is 
restored to its original condi- 
tion. The charging current is 
then cut off, and the battery is 
ready to produce current again. 
An efficient storage hattery 
must electrochemieally absorb 
the greatest quantity of elec- 
trical energy, with the araallest 
. , d lastly with the smallest possible weight It should 
la^Ie' of retaining its charge for long periods without 
loss. The battery should give a good return of energy. 
Other words, its efficicncv must be high, also it should 
a constant current, williout intermit ten ce, and should 
fily subject to regulation of current strength and voltage, 
function of the storage battery is sometimes misunder- 
Such a battery does not store electrical energy, cor- 
'S^aking, hut potential chemical energy, as tlie chemical 
f in the elements composing the battery, is responsible 
f production of current On discliarge. 
nrincipal storage battery in use today is the lead type. 
ii\y contains two electrodes, made up of lead peroxide 
0, and sponge lead (PbJ for the active materials, Tc- 
•iy. The lead peroKide-ia used for the positive electrode, 
j'^onge lead for the negative electrode. The appear- 
J'a complete cell is seen at Fig, IC, and of a set of cells 
itable use at ID. The two electrodes are immersed in 
s solution of sulphuric acid (H-SCj 
_a the battery is fully charged and In first class condition, 
Mtive plates have a dark red dish -brown or chocolate 
SAd the negative plates a light gray or slate color. The 
■ thus be distinguished one from ihe other, by their 
i also by the character 
\ve material composing 
(. lead peroxide is very 
p*6»pStone, while the 
, Jftfcrial is soft and easi- 
Urifcthe finger-nail. The 
F-'StiDstance is pure lead. 
It"*? .a spongy form by the 
J^. It has been suggested 
^SpOfige lead is a mixture 
■" 1 hydrogen, although 
I considered an allo- 
n <0f lead, which has un- 
4 a physical but not a 
i change. 

^discharge of the cell, the 
|tfe.' combines with the ac- 
ttUbces of the electrodes, 
Ige the active materials 
d< to their original con- 
_^ chemicals extracted 
ttvlectrolyte being released 
" led to the electrolyte. It 
; then, that the electro- 
Oity or specific gravity, is greatt 
iTitbe end of a discharge; and also that the 
'ha the electrodes expand as discharge proceeds. 
tlllit of capacity of storage cells is taken as the ampere- 
wKiii is usually hased on the eight hour rate of dia- 
- On this basis, a 100 ampere-hour battery would give 
iuoua dischargf of 12J4 amperes for eight houra; or a 
rpere-hour size, 50 amperes ior ?. \\om^. T>(vto.\«C\taS; 
Mhe 400 ampere-hour ceW, aVLO\i\4 aX-io 5>'*'ft-9^lT 




■is. Ic 
the end of a charge, 



I!^^^ 



I.. « ^mv 




n c, !,-D,„,^^ 



amperes tor 4 hours; ar 200 amperes Cor 2 hours; 
does not liold (rue in pran- 
ce. The ampere-hour ta- 
pacity decreases with an in- 
crease of discharge rate. 
The inherent capacity of a 
storage cell will depend 
upon, and be proportional 
to, the exposed area of the 
electrodes, subject to con- 
tact with the electrolyte, 
and also depends on the 
amount of active substance 
on the positive and negative 
plates. ^. 

Considered from a theo-(C£) 
retical standpoint, the^^-' 

weight of metallic lead on eitlier element or electrode, whidi 
duced to sponge lead, or to lead peroxide, required to prodtlH 
ampere-hour of discharge current ts .135 ounces, avoirduf 
' " ' ' ' ■. .• HI ^gjgfj 155 omiceH' 

active material neoet 
per element is from 
to six times the 
ica\ value, due to the 
thai il is impossibl) 
reduce all the active 
icrial. It has been 
:d that 
ipere- . __ 
charge at ordinary n 

of sponge lead an^ .5 
metallic T 
into pertK 

1 each element rea 
tively. 
The actual capacity of storage batteries is dependeni 1 
I of the electrode and the number of them on pan 
their character and make-up; the discharge rate and wt 
perature. All these important points have a bearing on 
resultant capacity, The S hour rate of discharge is conaiti 
standard for all si?es of batteries and a temperature o 
degrees Fahrenheit. The usual capacities obtaining in Al 
can practice, gives from 40 to fO ampere-hours per square 
of positive 
surface, whic 
found by multi 
ing the number 
positive plates 
llel, times 

breadth, limes 
as each plate . . 
two faces exposed 
to the electrolyl 
The change 
capacity of a. - 
is given below.j 
8 hour rate, 
Plante Plate.' 

8 hour 100%' 100% 

6 hour 96% 96% 

4 hour 88% 80% 

_ . _ 70% 61% 

t hour 48% 56% 

rif voltage of any storage battery cell is indcpendeitt of 
J'ijf of the plates. It depends on tiie ctiermcaX maVt-M^ ot 
electrodes, density of the electrolyte and Ae coti4\\;vQn tj\. 







as eompared to its charged or discharged state. 

'le ELM.F. or voltage of the lead-Sulph uric-acid cell, while in 

_»s of charging, varies from 2 to 2.5 volts, and on dis- 

iTgt it varies from 2 volts per cell down to 1,7 volts. Any 
degree or strength of voltage is attained by joining two or 
more cells in series, allowing about 2 volts to a cell. Thus, to 
suppl]r a line, requiring 36 volts, would necessitate using 18 
ceils in series. To compensate for the drop below 36 volts, 
or »riy other line voltage, a few extra end cells may be ar- 
rangea. so they can be swilciied into circuit and thus keep 
the E.M.F. up to the proper value. 

Storage cells can be bought nowadays at such low prices, 
that it does not pay to make thera for individual use. A very 
good liltle ceil supplying 2 volts and 10 ampere hours of 
energy is sold by the Electro Imponing Company, They also 
sell a 20 ampere hour cell. Boih of these cells are mounted 
in glass jars, with gas vents in top. The plates 
made on the best design, for hifili 
electrical efficiency and long life. The 
appearance of the cells is seen at 
I^g, 2, the former being the 20 am- 
pere hour cell and the latter the 10 
ampere hour cell. At the standard or 
8 hour rate of discharge the 10 A. H. ^ 
«ell would deliver l>i amperes for 8 , 
hours. The 20 A. H. type would sup- 
ply 2.5 amperes for 8 hours. Of course I 
these cells will deliver higher values 
of current than those cited for shorter 
periods of time, but somewhat in the 
ratio aforementioned; the energy de- 
livered being smaller than normal if 
the discharge rate is increased. A smaller 
normal may be taken from the cell for ; 
longer period, as '/i ampere for 20 hours 
1 ampere for 10 hours, etc. A table of varic 
cells and their capacity in lighting lamps i 

A set of several cells connected in series is 
mounted on a wooden frame. 




Big. 3 



I correspondingly 
'; the same as 

; E'ven below. 
seen at Fig. 8, 



ted by the cut 
1 series and delivers a 
ind 60 ampere-hours of 



The Electro ignition storage battery is 
Rg. 3, This is composed of 3 cells an 

Steady and powerful current at 6 volts a.._ ._ _ ,,___ ,_ 

energy. It is also made in the 6 voh, 40 ampere-hour size. 
Any size of plant can be built up out of several of these units 
on parallel or in series. Two sets in series would give 12 volts 
»rid 60 ampere- hours of energy. Two sets on multiple would 
supply 6 volls, but 120 ampere.-hours of electricity, et Cetera. 
Storage cells are at once the most economical and satisfac- 
tory solution of the small home or laboratory lighting problem, 
all things considered. They can be easily charged from pri- 
mary cells of the Edison or Gordon type or from any other 
direct current source, as from a dynamo. Alternating current 
cannot he used to charge storage cells directly, but by the 
I interposition of a rectifier of the iron-aluminum (see lesson 
No. 4) type, or by means of a Cooper-Hewitt mercury vapor 
converter, the A. C. mains form a ready source of charging 
eurrent. A motor-generator is often employed to charge the 
battery with also, the motor running on A. C and the gen- 
erator unit delivering the necessary D. C. for charging, (See 
lesson No. 8.) 
I One of the most important elements to be considered in 
I storage battery operation is the electrolyte and its spccifii- 
I gravity or density. This varies with the condition of the cell, 
as compared to the amount of charge or discharge energy. 
The density is measured by an instrument called a hydrometer, 
one form of which is shown in Fig. 4, a glass >ie?,5«l \ie\a^ 
LjBrnished with it to float the instturcveT\^. wVfcw W^ei -«\*\ -i 
■■MBpfe of the electrolyte. In large vjotV vVie, V-jiic 



ind this is the best ti 



I strikes t 



i-il in ihe cell ilst 
1 readiHK generally. 

The hydrometer floats a 

in the citcirolyic at vari 

reading being noted on 

I instrument at the point ' 

I of the electrolyte solutio 

I drometer stem. 

There are Iwo scales ir 
I hydrometers; the specilic gravity e£a£v4 
I the Baume scale. The specific gravitj-W^ 
is rnoeC used, and is divided np in two H 
Some hydrometers, for instance, in»y t 
1.2 Sp. Cr. meaning that, al tliat scale 4 
sion, the density of the solutJou &>^^I 
I hydrometer, is such, that it U l^tl^ 
I density of water. Other scate; .'Kp" 
perhaps, 1,200 degrees Sp, Gr, vfM 
equivalent of 1.2 Sp. Gr. but ' 
certain work to jjermit of closer readings, bein 

Floating a hydrometer in the electrolyte and notu^J 
surface reading, does not mean that the density indicolef' 
what it should be. The density varies directly willi.(lie4 
peratirre of the electrolyte, and so it is always corrcc^^ 
some standard temperature, usually 70 degrees Fahrenhfut^fl 
all commercial practice. " ' " 

The density^ o 

• =n ~^ cific gravity is 

) MO vours. D,C. than Dormal_ Ht^) 

temperature IB f 
standard and h_„ 
than norraaL it. \ 
temperature is >** 
standard, (say J, 
grees .Fah.)j „ 
the density dec^Cfl 
with increase oE b 
perature, and vT 
verea. The caeiRcient of change in Sp. Gr. for one i^ 
change in temperature Fahrenheit is .32 degree. Hence i 
hydrometer indicated a density of 1,200 degrees, ai "" ' 
Fahrenheit as taken by a floating thermometer i .. 
trolyte, then the density corrected to 70 degrees Fahrenhd™ 
standard must be lower than 1,200 degrees. 

'See SCandatd Eleetricid Enainee 



I [o & 



<"><■<"> - '!''; 



difference between standard or 70 decreet Fahrenheit 

e observed temperature or 54 degrees Fahrenheit, is 16 
Hence 16 times the change an Sp. Gr. per degree, 



1 density of 5.!2 degrees. 





ejves 3 subtraetivi 

the density corrected 
degrees Fahrenheit is 

degrees minus 5.13 
is'or practically 1,195 
ea. It this observed 
\y had been 1,200 de- 
at 16 degrees Fahren- 
ibove standard, or 86 
ts Fahrenheit then the 
ition coefficient for 
orrected density at 70 
!S Fahrenheit would 
4jeen additive, or the 

r. would have bfen 1,200 degrees plus 5.12 degrees or practi- 
,20S«legrees. In these readings, if the fraction is .5 or more 
sited one degree. In the above it is only .12 and is dis- 

liectrolyte can be prepared by mixing S carta of pure 
id water and 1 part of pure sulphuric acid (acid made 
sulphur, not pyrites as this contains iron moBt always) 

' - '^' - • ■ always be poured slowly into the 

Tieanwhile with a glass spatula or 
rod. The mixmg can be dione 
in a glass, earthenware, lead, 
or enameled vessel, thoroughly 
cleaned out. When first mixed 
considerable heat is produced 
Offing to the difference in the 
densities and make-tips of the 
two fluids. The electrolyte 
tiinst be cold before filling the 
cells, or else the plates will be 
I wfth a white precipitation, and is termed' sulphating, 
practically puts the battery out of commission, unless tire 
. arc removed and the sulphate scraped off, or srill better 
llphate.can be removed by a quick overcharge carefully 
iatered sometimes. Charging has to begin soon after 
ectrolyle is put into the cell, 

battery gases quite violently, while worldng, and to coni- 
^ for the evaporation of electrolyte in this manner, a 
i^Kr Is added from time to time as required, to keep the 
lUways covered by at least ^ inch of electrolyte. About 
i^ months or so, a little fresh electrolyte or acid is 
to the cell to keep the density at the proper figure. 
"ebsity falls on dis- 
ig riie cell, but re- 
a former value when 
■ed, the range of risa 
jr varying from 100 
j .tO' 200 degrees Sp, 
k usual discharge 
value is 1,120 de- 
In lead cell practice 
itn the recharge t^ 
'On^ until the dcnsilv 
i lj200 degrees or 
Sp. Gr, The 
, ilsQ watched 
rand charging is gen- 
- complete when the 
Wr in the charging 
"registers 2.S to 2.6 
m cell, with circuit 
and about 22 volts 
J mtb circuit open, 
is ot voltage have 




M W 



no practical aigtitficance wIicd taken on open circuit, h j 
cell's E. M. F. drops as soon as the load is, put on it. A[ 
10 per cent more voltage than that given by tfte cell ts reipi 
of the charging machine, but ihts is varied so 
keep the current in amperes at a certain value. 

illustration, on a 400 ampere-hour battery, which 

SO amperes, normally for 8 hours (8 hour rate), the chaf 
rate is about the same, i.e., 50 amperes are put 
it for a little more ihan 8 hours, on regular charge, 
initial charge on this battery was of 2,500 ampere-hourt V 
to form the plates. The initial -charge was started on an „ 
trolyte denstly of 1,250 degrees which, on closing the chaigiaj 
switch, immediately dropped to about 1.130 d . ■- - 

From this value of the Sp. Gr. it slowly increa^ 
ing current at 50 amperes constantly, until ten con^ 
and similar hydrometer readings were obtained, when lii" 
was stopped. The duration of the inilial charge ws- 
40 and 50 hours; current at 50 amperes. Regula: 
thereafter wt . . — . r . „ . 

the density i 

in the hattery circuit is shown at diagram Fis. 5A, 
SB. depicts the connections for a voltmeter VM, with s 
cell SB. 
Great 



rapid deteriora- 
tion in the life, 

ctiit. which 
would cause 

terious harm. 
and probably 
rmn the cell 
completely, dis- 
integrating the 
active material 
composing the 
plates. 
The state of charge 




color and the negali 




F>g. 5 tiepic 



a cell can be fairly judged 
by the color of the positive 
-Jve plates assume a dark choc 
light gray when nearing full 

On discharge the 
sity value is a very '^ 
gauge of its magnitil 
as the density or 
Gr. falls in direct pre 
pDrtion 10 the ampere- 
hours taken from the 
cell. 

Ill large battery In- 
stallations, a charging 
rheostat or variable re-" 
sistance is used in seriel 
with the battery and 
the source of current 
For charging small 
cells, it is often con- 
venient to connect thent 
up to a D. C. light eir-; 
cuit, with a few incan-, 

P^ug*' descent Um^s in se;^ 

or series mM\u-p\s; ■ "** 

wiring iliagra,m loi t.\ie t^vw^vns 



1 



SllB . 



Multiple a 
volt ^cH?. '^i 



I cut of a charging b 
cliarge a 20 ampere-hour 
it, about four 16 candle-pi 
: lamps, passing J^ ampere each, may be used 
Ic as shown in the diagram, allowing ihe battery to 
: 2 amperes for lO'll hours. This may be increased 
i;s of urgent necessity, giving ihe battery 



f the batterj;, 

marked with a plus 

+) or a red seal on it, 

lie way to ascertain the 

r of the circuit, is to dip 

ipositely charged wires 

iss of acidulated or salt 

The wire from which the 

as bubbles are evolved, 

legative pole, Pole test 

very handy for this 

as also is the liquid 

indicator sold or the 

, A voltmeti 



ir ^^^H 
■pow«^ I 



igher rate or current value for a shorter period, 
arrangement of the cir- 
chaiging must be such, 
:e positive pole of the 




hand, forms the best way 



arity, providing it is of the permanent magnet type, such 
Wt^ton. 

9tige cell should never be discharged below 1,7 volts, 
fter.yel. not below 1.75 to 1.78 volts, 
^TWnes it is desirable to put a storage bailery ovt of com- 
'foT a while. This is accomplished by drawing off the 
yte as follows: After giving the battery a complete 

siphon or pump out the electrolyte into carboys or 
led vessels, which have never been utilized for any other 
'V^en each cell is emptied, fill them up immediately 
lean water, and when all the cells are filled, start dis- 
ig Ihe baltery, until the voltage drops to about I volt 
bonnal load. The water can now be withdrawn. 
tart Mp ail idle baltery, fill the cells with electrolyte, and 
irge at normal rate; 25 to 30 hours constant charg- 
._ _ _ required to give a complete charge. 
ige cells are a very useful electrical utihty, but they 
be treated intelligently, if the best results are to be 
:d of them. In the cut Fig. 6, is shown a portable 
! cell for a carriage light. A storage cell adapted to 
t portable shop light, and suitable for watchmen, photo- 
dark rooms, etc., is depicted by Fig. 9, while cut 10, 
a storage battery lighting outfit for bicycle use. 
UMMARY OF STORAGE BATTERY DATA, 
ge batteries are made for either stationary or portable 
Both positive and negative plates are of pure lead 
. local action is reduced to a minimum. This feature re- 
a high efficiency, long lite and ability to hold charge 

a long period of open circuit, 
mechanical de- 
of the plate is 
that the activ 
al is in a thi 
supported by 
rtor, and ac 
□ the current 
ilyte. Provtsi 

within the pi 

,le itself ti 
idatc any di 
= Ihe 




Tlicrefore, Ihe haiiery dinchArgc volt»ec w the number of •., 
in scries tnulliplied by twu. The amiitfc tiuur capacity, t 
rate of discharge and tlie rate of charge of a balteiy an 4 
termined by the die and number of pbtes in a cell. 

The voltage required (o charge a mH varies froni 2J i 
at tile beginning to as high as 2.S volts at tile end, t' 
charging at a constant current, usually the S-hout i~ 
rale. The diarging current 13 usually controlled by X 
in series with the badery, boo ■ ■ 

control. 

The maximum liae voltage Jo he provided for i 
Riven number of cells in series is the number of ce!I4 
by 2.8. The charging current will dejiend upon 1 
Ibe cell 

When a cell discharges, the electrolyte (sulphuric 1 
tion) forms the active material into lead sulphajf 
comes Weaker in acid with an increasing _ per .cetf* 
and conversely, on charge the sulphate is dhilhg 
acid. A definite amount of sulphate is formed for eaj 
hour discharge, therefore, the density or spedSc J 
the electrolyte changes a given amount 

This change in specific gravity of the electrolyt 
lional to the ampere-hours output and is practically a 
of the rate of discharge. A very conveiiient an. 

method of charging is available by using a hydromete. 

ure the change in specific gravity between the conditions of P.... - 
charge and full discharge, and then charging until the originBl I 
specific gravity of the electrolyte is reached^ \ 

The energy remaining in a cell at any time during a dis- 
charge can be found by noting the change in specific gravity of 
the electrolyte from the value at the beginning of the dis- 
charge and comparing it with the total range for the given 
disdiarge rate. 

The range in density of specific gravity of the electrol; 
between full charge and discharge, at the 8-hour rate, is appra 
mately from 1,200 to 1.160 for a standard cell in a glass j 
the temperature being ?0'' F, The range will be approicinii ' 
from 1,200 to 1,180 for a discharge at the one-hour ratel 

The exact change in gravity Ehould be determined for e 
particular size of cell as it varies with the ^ize and the ni 
her of plates. 

The normal ampere-hour capacity of a cell is based 1 
the 8-hour rate of discharge and is arbitrarily taken a 
Wheji taken, at other rates the ampere-hour capacity i.j._ 

The available ampere-hour capacity varies with the todi 
ture and rate of discharge. For a limited range of ten) 
ture at the 8-hour rate of discharge, the capacity varies agp 
matcIy one-half of one per cent, for each degree Fabrefl 
change in temperature above or below 70° F. An 
temperature will raise the capacity and a reductioi 
it The lower the rate of discharge, the less will be Jbe y 
tion due to. temiierature. 

Storage batteries may be used to great advantage in maui- J 
taining a constant load on a generating system when ilie load 
factor is poor. A sample of such regulation is shown in re- 
production from recording ammeter records of a battery and 
regulator maintaining a constant load upon the generating systeni 
with an exceedingly variable external load. 

When it ie desired to maintain a constant alternating-current 
load, the same degree of regulation may be obtained as in 
direct- current work, by connecting the battery across the direct- 
current side of a boosted rotaty converter controlled by the 
regulator, 

SOME DON'TS. 

Don't nm each celi below 1.8 volts. 

Don't wait long; to have it recharged. 

Don't test it with an ammeter alone. 

" ' " a screwdriver or file across 



Don't lay 
it spark. 
Ehn't recharge with alternating eutre?t. 




Y\ie cotiYvctUona 



G the wrenelj to tigliten binding posts. 

ios ft lighted cigar near a battery during the chuge. 

^FUL RECEIPTS AND HBUORANDA. 

J Popff- — Make a thin solution o£ white starch and 
xipt o£ thin white blotting-paper in it, and set aside 
, Jean jiiacc to dry. Dissolve J^ oz. of polassiuin 
MH 1 pint of water. Immerse the strips in the solu- 
pr s lew seconds and again dry. This ^aper, wbeu 
Hied and used in the usual way, turns violet at the 
-kpole. 

\ good varnish is made of 1 lb. of shellac dissolved 
pit M polisher's finish. It farms a tough, coherent 
"ad adheres strongly if the article to be coated 
J before the varnisn is used. <It is best to apply 
i or three thin coats, allowing each coat to dry, 
13) In one thick coat. 

«OTinrf.— Equal parts of beeswax and resin well 
.a used hot. 
SCnuHt. — A good cement is made for Leyden jars 
"plating stands: Sulphur, 100 parts; tallow, 2; resin, 
', HJelted together until of the consistency of syrup, 
Jficient powdered glass added to make a paste. This 
S must be heated when apphcd, and will be found to 
mast acids. 

iiA^Pare India-rubber (cut small), I part; coal-tar 

% 12 .parts; digest in a covered vessel with eentle 

"f agitation, and when thoroughly dissolvef add 

I" shellac 20 parts. Continue tlie heat and stirring 

ct litiuetaciion has taken place and pour the 

, while still hot, on slabs of polished metal or 

s to form thin sheets. When required for use 

iron vessel to its melting-point, 248° to 250* F. 

»ly in a liquid state with a brush. It can be made 
9 requirid by increasing the proportion of shellac. 

STORAGE BATTERY TERMS. 

(for practical work) of electric current 
—A practical unit of quantity; being the quantity 
iiiBUrrent of one ampere would carry past a given 
|i>sne hour. 

%. term, whoae meaning is evident, technically ap- 
> tbe distortion of accumulator plates by badly dU* 

\ black, hard preparation of India-rubber (Vulcanite.) 
' — The conductors by which current enJcrs and leave} 
' ' — Anode =r entering; Cathode ^^ leaving 

lliemical decomposition caused electrically. 
r-The conducting medium between electrodes whicH 
f electrolysis. 
- --.V g electrode of a cell. 

,_ .1 for electro motive- force (see above). 

stceleton framework of an accumulator plate. 

we. — An oxide of lead whose chemical symbol is 

oad protoxide; PbO. 
jaA lead ; Pb=0.. 

tPcfe, terminal, plate, etc., the pole, terminal or plate 
i.t. ..._ — rrent returns to a generator or leaves an 

t'lmit {for practical work) of electrical resistance - 
Tvalent to terminal. 

r Paper.— Used for determinating the positive and 
^ poles of accumulators. 

The converse of "negative," i.e. "outgoing" as applied 
Bierator, "ingoing" of an instrument. 
Linstrumtnt like a spoi-n with a ftaV WviV. 
e connecting screw by «\ncVi a con4iic\.oc xs ciot 



^ \it reatlilf pcrceiTsd by looking at the current 
^TIB d«picicd at Figs. 2 and 3. In Fig. 2 is seen 
[ular curve at tlie top (or an allematin^ current, i 
Ig ilj direction from positive to negative periodically; 
—" number — _ 1 



irctsals . 
The di- 

irrent wave 
resultani 

insei^ng a 

reelifier cell 
ahcmaling 

; circuit is 
at die bot- 
Flg. 2. It 
tbit die di- 

ilsator)' and 
tient, liav- 

londin 



Uoiii 



tey- 




riG.e 

a poor efBcieney. 



the recti- 
ta not operate. This .. ,___ .. 

ivercome this disadvantage, the four eel! type of reciiner 
veloped, as aforementioned. The resultant direct current 
inn, tjcturring from its connection in the A. C. circuit, is 
the bottom of Fig. 3. Here it is evident the efficiency of 



Ition is much higher, in fact 100 per 




higher, than 
with the single 
cell type, as 
there arc two 
direct current 
pulsations now, 
for every cycle" 
of A. C. o'e 
there is one 



The 



Ele 



0.Q 



trolytic rectiher 

is based upon 

the well known 

principle that if 

a n aluminum 

and iron plate 

eleictrolyte, thecell so formed 

direction, but practically none 

the opposite direction. Hence the 

CHARGING STORAGt 
BATT 



w 



RESISTANCE 



FIG.4 



i 



yi Ute rectifier on an A. C, drcuit is to^lip off the reverse 
■aire of each cycle, and allowing only impulses of i 
Ctiorial character to pass through the cell. The aluminum 

It forms Ihe cathode or negative electrode) will not pass 
■Bit can pass from the i r o n to thei o»»«ft, ^^l^». 
am. From this it is seen that iS a. tt«i&M dot* ■oW.'WOT'st 

is only necessary to reverse iu coivnettvaoa. t\\»; «».- 



_ o( the siDgle cell »n<l the ioai cell types of *leci._ 

rccti^er are shown diagramiiiat!call)[ iii Figs. 4 anil 5> Then) 
live— D.C icnninaU fcpr«scni Ihe binding posts on the aluinil_ 
electrodes while tlie jiositive + O.C. terminals represdU U 
binding irasts on tlie poliahed steel, or Icud dectrodM. 71. 
efikiency oi the fr.ur cdl type is given by the rnanofaclunl 
(The Electro Importing Co.) at 8S per cent. This t "' 
pus u mucli 3.i 5 amperes, and ccmtinuously as in . ._ 
storage cell» at 2.5 amperes. The one and two cell t}[pca BL. 
about 1/3 of the above current. The electrolyte bath in wlffi 
the electrodes are immersed can be of several differe nt tf ^ 
shions, but a. very good one is a neutral solution of af 
phosphate in water.* C. F. Burgess and Carl m 
(Transactions of the American Electrochemical Stid^ 

A^C^ 



>--RC SI STANCE 



'O fOr 



inoN 



® 

I fused dec 



'AL 




D-C MOTOR 

>lyte of molten sodium nitrate, with an alumiinl 
ana an iron dectrode. A saturated solution of bicarbonate 
Boda is also a very good .dectrolyte mixture, and is tniieh tt 
for lurge X-Ray transformer sets. I 



Transformers. Taking up thi 
be said that in general there ar 
in use, viz., the open core and dosed 
former, in its simplest definition, is 
-onvert or transform the E. M. F. 
CORE OF 



cult, into 
different s< 
of values o 
the 



SHEET (RON^ 



200V.A.C. 







separate and 
distinct cir- 
cuit The 
cut* Hg. 6, 

depicts sche- 
matically a 

transformer and its parts, and 
operation, 

A transformer, o^ the form shown in Fig. 6, is of lh< 
core type, i. e„ the iron magnetic core is continued on 
forming a closed magnetic circuit, and giving much 
efficiency than the open core type as in Fig. ?. 

The action of the transformer is as follows :— An altertkai^ 
(or sometimes a pulsating, as in the induction coil) ctirreiit 
supplied to one coil or winding on the iron core, marked print 
con, and the current traversing this winding, sets up or cres' 
a powerful magnetic field of varying strength and jjolarily, ( 
sponding to the changes and variations of the primary cii 
This fluctuating magnetic field continues around the iron d ,. 
Tn doing so, it also simultaneously creates a magnetic field in't 
air about the core as well. On the other limb of the core t 

f the Inteniatiooi,\ E\«;^tiwiV Caw[i*M, 



^.v^urji* »f 



r reverses itself, it sets up in this second or secondary 
winding an electric current, 
jNOAHv whose voltage is dependeat 

'"""^ \ upon the number of turns oi 

iOA^J-^wSh*™ ""^ '"^ ^'' ^^ compared to the ■ 

K^ZZj*" number in the primary winding. 

■ ^"^^ 1 @ If the transformer was de^ 

c»,iMau signed to have the voltage re" 

14,7 lations existing in the diagram 

Fig. 6, then to have the sec- 
farr coil deliver 2,000 volts, from 200 volts in tlie primary 
1, -would recesalate the ratio of the turns in the two coiU 
e., the secondary coi! would have to have 




Fig, a. 

J>olts. Thus it i=, that the ratio of the primary and s 
' voltages depend upon the ratio existing between the 
' wires in the two separate codls. 

J example, it the secondary 

! Bopjilying 10 tiines the' primary 

■ 1 It would supply only 1/10 the 

r current in amperes, theoreti- 
s the total watts,* in the sec- 
circuit could not be greater 
ihox in the primary circuit. In 
Btice, however, the efficiency of 
t&sformation of large closed c 
isformers is extremely high, 
o 99 per cent, oftentimes. 

> cer cent. A slight loss 
1 of energy is occa- 
iron core, and also in 
e windings. These are 
: technically as the iron loss 
jfper lots. The iron loss is due 
pally to hyslereiis or apparent 
Sc friotion, occa-aioned iby the 
les of iron refusing to quickly 
* the changes in direction of the 
efizing current. It is para- 
It that the primary current must 
in strength periodically or in 
1 and direction both, to c 
ng magnetic flux ii 
rl eurrfnt would only c 
Uiging magnetic field, wher 
i cotinected to and disconnected 
n the primary winding. This is t\ie ^tiwd^^e c'i \\\t \i-mS\m 1 

- product 



k- tiansformatio 





Vis. 10. 



induction or spark eoU. A vibrntor or olhcr fndrrnipeer. ( 

eally makps and breakx the prtmary drcuii, lesulttng ir 

Biktmg direct current passing 

through it. This caiises the irou 

tore to be magnet izcd and dc- 

fnagncliziil Tapidly, and in con- 

'Bequence the seoondary coil ban 

Induced in itself, a cnrretit i 

similar frequency to thai ill tl 

l^rimary circuit. Induction coi 

invariably have an open core < 

magnetic circuit as shown ; 

Fig. ?. They are considerably | 

lets efficient tbaii Ihc closed 

core type of design, in that the 

magnetic flux leaves the core at 

each end and completes the mag- 

«K«e - circuit through the air. 

which offers a very high reluctanci 

of energy transformation in the optn 

exceed 60 to 70 per cent. The voltage reiaiions are tne aa 

as in closed core transformers. 

A cut of an open core transformer is seen at Fig. 8^ t_^ 
particular one being called a transformer coil, and used f0 
Eteppii^ up the voltage of a 110 volt A. C. or D. C. circuits 
aeveral thousand at the secondary terminals. It is used ib 
■ wireless telegraph purposes, in connection with a Ge 
tleetrolytic interruplff. An induction or spark coil is a 
former of the open core type. A 1 inch coil delivers a i 
spark from the secondary winding at a voltage of i 
20,000, from 6 volts in the primary circuit. 

Referring to the Gernsback eteclrolyltc inUrrupler, mW-SttXit 
above, as used in connection with the transformer coil, its^'i 
pearance is seen from Fig, 9. It consists o£ a glass jar contailUn 



lOAMg 




ly where 
four cell tj 
s_ also connected in circuit as the interrupter operates best 

The interrupter itself is well build having all the electrod 
connections sealed in a porcelain cover, so that they cannot "b 
attacked by add. The special rod at the centre sets in a porc< 
lain tube with a constricted lower opening, and the gas bubble 
formed electroljrtically at the point of the rod, serve to make sQ 
break the circuit. The frequency of interruption developed ll 
this instrument is enormous, reaching 5,000 to 7,000 per secooi 
The interrupter causes the secondary winding to dehver a ver 
heavy current, resemhling a flame, and also works i 
advantage on spark coils. 

The action of any transformer is quite unique under difTeren 

eontJitioas, and some of them will be considered here. 

It A transformer, of either the open oi dosed cotc t^v^ i 

eoaoccted to an alternating current circuit., 'mft One s6coi\4a 

34 



tttng open, it will take a veiy small current from the circuit. 

(is due to the fact that the primary coil magnetizing current 

b reacts upon itself, that the reactance effect gives a greater 

Psistance to the coil. The reactance is in the form of a counter 

' bucking E, M. F. and hence tends to lower the effective 

, M. F. passing through the primary coil. So, while the 

■condary coil is open circuited and not connected to any load, 

! transformer primary winding consumes very little currentj 

^.e to lis reactance or self-induced counter E. M. K 

tWhca the secondary coil or winding is connected to a load 

me kind, it will immedbtely begin to deliver current to thai 

Consequently the primary winding must be taking more 

Brrent from the supply wires, and it does, in direct proportian 
\ the secondary load. The passage of current through the 
Kondary winding is in opposite direction at any instant to that 
I the primary, hence the magnetic reactance of the primary coil 
""I some extent counterbalanced by the magnetic field of the 
idary winding, and the primary current is therefore greater 
kproportiDa to the load on the transformer. If the secondaiy 
nbdii^; is short-circuited, the transformer would pass so great 
_ current that it would be burned out. 

■Transformers are known either as step- up or step-down, 
pcording to whether the secondary winding raises or lowers the 
voltage. This, as already explained, is dependent 
. e ratio of the turns of wire upon the respective coils. 
Bcprcssed in a formula, it becomes:^ 
Secondary turns 

K = . 

Primary turns 

! K is the ratio factor. If a transformer contained a 

icDodary coil with 100 turns and a primary coil with 2,000 turns' 

Ees the ratio of transformation would he 100 divided by 2,000 

3 1/20; or the secondary voltage would be 1 /20 of the impressed 

BBUtry E. M. F. This transformer would belong in the class 

T Btep-down types. 

Of the transformer just cited was, say, of 1 kilowatt* capacity, 

1 ft closed core, and an efficiency of 80 per cent., then to get 

diowatt output at the secondary terminals, would require an 

nit at the primary terminals of^ 1.2 times I kilowatt or 1,200 

Etts. The secondary voltage as remembered is to be 1/2D of 

s primary E. M, F; which is taken at 100 volts. Hence the 

idary voltage is 1/20 of 100 or 5 volts. The secondary out- 

' "X watts or 1 kilowatt, and so the secondary current in 

vill be 1,000 <Mvided by 5 or 200 amperes. 

B primary voltage is 100; total input at full load 1,200 watts; 




FIG. 12 



_,r current input consequently 1,200 divided by 100 or 12 am- 
Wfi*l this allowing tor the loss in efficiency of trans fbniiation 
Ba to iron core and copper losses. 

'The primary and secondary wires are designed of sUch size 
t they contain 1,000 circular mils of cross- sectional area for 
\ ampere of current they are to carry. From this, the prtmarv 
e would require to be of 12,000 dttvAai m\\* atvi 'Oft.t %*.wreA.- 

1*1 Ul»iratt it 1,000 mts, or 11/3 bDiacvQwCI. 



■17 wire of 200,000 circular miU. The size of wire correspon 
ing to thM« area* can be taken from any etandacd wir« tali 
tuch ai the "Brown and Sharpe," cr "Ameiicun gauge." T 
si» of wire corresponding to an area of 12,000 dr. milt- 
No, 9 B. & S. copper wire, whose area is 12,99(5 dr. mils. T 
nearest correspon dins site of secondary wire having an arM 
300,000 dr. mils is No. 0000 B. & S. Gauge copper wire, T 
wire for transformers is usually double cotton covered. T 
proper size of iron core for this 1 K.W. transformer opent^ 
on too volts, at 60 cycle frequency, is 15 inches by 8U indiM. 
2 inches thick. The width of the legs on any one of the ta 
sides of the rectangle is also 2 inches. For a change in vofes 
on the primary mains the number of turns on the primary' C 
would be changed. For a change in the frequency of the pitn 
supply current the iron laminated mass would also chaogCt 
coming less in quantity as the frequency increased, and ' 



and more primary current for a given secondary output muK 
put into the transformer. 

A step^up high tension wireless transformer of 1/4 

capacity is illustrated by Fig. 10. It is 3ubstantially_ built, 
mounted in a wooden cabinet, with terminals of primary 
secondary windings on the exterior of the case. It opetat 
on 110 volts, 60 cycle A. C. and delivers 15,000 volti and a |r^ 
tion of an ampere at the secondary terminals. Wireless ' 
formers of the closed core type, such as the one just da 
or the open core type, have largely superceded the spark fii 
for charging the condensers and aerial wire as they are nu 
constant and reliable in operation and give a very heavy afiqt 
age in the secondary circuit. The efficiency of the transforn 
in contrast to the induction coil is quite different too; thie lal 
being approximately 20 per cent, or more, less efficient than 1 
former. The transformer can be built in any, desired size a 
cjicfates very successfully in the larger form, while large indi 
tion coils are very expensive and also hard to operate propff 
in the big sizes. 

While discussing transformers, the anlo-transformer of rin 
coil transformer must not he overlooked. The schematic 
rangement of its various sections are portrayed in Fig. 11, 
observed, there is an iron core of built-up sheets of tliin antiG 
stock, as in regular practice, but only one coil is shown. "3 
coil may contain, say 200 turns of wire, for example. < . 

The single coil has a part of its turns in use for the p^ 
winding and a part of them for the secondary wiHdiiK't<rfi 
transformer, as indicated by P and S respectively. We . 
take the seclion P, or primary coil, and have it embrace, say, i 
of the 200 turns of wire on the transformer. The secondary, ( 
S turns, may be taken at 50 turns, or one-half the primal 
number. 

The number of turns on the single coil of an auto-traosfom 
is the same as would be required if it were employed esduMV 
for the high-tension winding, and a separate additioflal e._ 
were provided for the low-tension winding, When the ratio I 
transformation is 2 to 1 or 1 to 2, the amount of copper • 
the one coil is exactly the same whether it is used, as < 
aulo-trans former or as a high tension coil of a regular tt 
ctril transformer of the same output Less copper is reqmri 
for an aulo-transformer than for a two coil type, also less ir 
is required to surround the copper. 

Referring to the diagram, Fig. 11, it is seen that the siiu 
coil is designed to carry 10 amperes throughout (consideiv 
a 1 kilowatt unit) and for a total voltage of 100. The voltil 
per turn of wire throughout is identical, so if it is desired ' 
obtain 50 volts on the secondary side, it is only necessary ' 
connect the secondary lead wires to any two points on the cOi 
tinuous coil, so that but one-half of the total number of tail 
Vj embraced between them. Also M a secDn4a.tY t. M. ¥. ol * 
Volts was required, the secondary \ead "Hires staoMXi en&ni 
5fl 



W/lOO or 1/4 of the total tnrr 
^ondary current is 20 umpete 

owatt) at 50 volts, and is opposed iu umc yniiai: ^uniaun uf 

i saperposed 10 amperes of primary current, so that even in 

if part of the winding, the resultant current is only JO amperes. 

The auto-transformer is very efficieoi for certain voltage 
ratios and exceeds that of the two coil type, besides requiriiiK 
less material in its construction. Auto-transformer* are Used 
for a variety of purposes chief among them being, to control 
the amount of current supplied to alternating current motora 
while starting, and also for speed regulation ; balance coils, in 
2 wire to 3 wire supply systems; tuning coils and helices in 
wireless telegraphy; reactance coils; etc. 

Auto- trans formers are used successfully and to advantage in 
operating singk-phase electric railway motors. They are used 
hore to supply low voltage for the motors from the high voltage 
supply wires. The auto- trans former a are arranged in this case 
with nine intermediate tow-potentia! taps, and are used on 
locomotives and motor cars, with the Ime wire potential at 
11,000 volts. The employment of auto- trans formers in this ca- 
pacity was dictated more by convenience than by economy, 
although an auto- trans former with a ratio of 22 to 1 as used 
here, would be a trifle less expensive and more eflicient in 
operation than a two coil transformer for the (ame purpose. 

In general, the following features are the principal ones, in 
the construction of modern transformers: The cores, for cer- 
tain sizes and designs, are often made up of a. quantity of 
diarcoal annealed iron wire, such as Norwegian core wire. It 
must be 33 soft es possible, otherwise it will lower the effidenqr 
of the transformer. For low voltage types, not exceeding 50O 
volts, Empire cloth may be placea around the iron core to 
instilate it from the wire coils to be placed over it 

For low tension 110 or 220 volt primary windings, the wire 
can be double cotton covered or enamel; if the former it should 




Fig. la. 

be well shellacked or impregnated with wax, or, better stilL 

I soaked with some good insulating varnish or compound ana 

ijced until the compound has permeated all the pores in the 

The secondary windings can be similarly made up, as above 
Veictibed for ordinary low voltages. Common practice is to 
'~'n>erBe the whole transformer in oil. such as transit oil, 
"^ne oil, or double-boiled Hnseed oil. The oil used should 
3 high flash value. For voltages over 1,000, it is recom- 

ided that the transformer windings and core be oil insulated, 

M)t the practice in wireless transformer building seems to be 
~"'ee them thoroughly portable, and so oil is not used in 
^nerally. In place of the oil a wax-rosin mixture is 
. over the transformer when it is placed in its ca^net and 
n^ seem to stand up very well, notwithstanding that the lec- 
Onoary potentials often reach 50,000 volts or more, In these 
'*'"■«• of transformers, the insulation is kept up to a very 
^1 standard by subdividing the high tension winding into a 
._mber of smaller sections or pies as they are nidcnamed. 
hdi pie is well impregnated with hot paraffine or beeswax, 
jiott or after winding. 

■In tiie designing of open-core transformers, used mosttj tii^ 
*rries9 purposes, with higli poteT\Ua\ Mcotiiat-j toA'i, "A \* ^»^^■ 
^lace a mica, fibre or hat4-TU,'b\i« wSit (iV wytviv^wMSg 
! over the primary windins at\i wixft, <a'Cp.«^'**- '^ 



cUscharge of the seconilary will take [ilace into the primur « 
core, inslead of between the secondary terminats. 

A small transformer it often employed (or ringisc t ^ 

running electric toys small motors, etc., and tlie appeanact KM 
one of these is shown at Fig. 13, while Fig. 12 illuatrilei del 
connections of the two -windings, primary and secondary. TIkS 
piimary coil is connected (o a 110 or 220 volt, alternating 0U^■ 
rent circuit, with fuses as indicated. Several voltages majr br 
obtained from the secondary coil, bj^ connecting on to di0er 
numbers of turns, suitable leads being brought out to bind 
posts. These transformers consume practically no curff nt jf 
the A. C mains, and take the place of troublesome battf^" 

One of the largest, and probably the largest, use pf^ 
dal transformers is in the stepping up of eencrstofi 
for long distance power transmission, and stepping q 
high tension current of fetd wires or primaries tot 
one for operating incandescent lamps, motors, : ' 
other pieces of apparatus in the home and wi ... 
transformer and alternatiii); current have made elec$ 
great master it is lo-day. 



LESSON No. 5. 
SMALL ELECTRIC LIGHTING PLANTS." 

THE small electric lighting plant which is usually is 
lated or away from any ordinary sources of curr« 
supply, has grown to be legion nowadays, thanks 
the .wonderfully developed gasoline engine, and I 
simplification of the electric generating apparatus. Ev( 
farmer can now have his own electric plant, and it will CL, 
idia practically nothing in most instances, especially wtte 
water-pcnper or ivind-milli are at hand, with which to drive, 
dynamo. Failing these facilities in the line of prime-movH* 
or driving power, a gasoline or kerosene internal exploit^ 
rngine is quite che^aply procured, and often to do duty f ^ 
driving odd machinery around the place, and the dynai.. 
simply absorbs power during the idle moments, to charge 
storage battery floating across the line wires leading fro 
the dynamo. In this arrangement an automatic cut-out mD 
be inserted in the line so that whenever the dynamo volta| 
falls belorf that of the storage battery on charge, it W 
automatically disconnect the battery, otherwise the battel 
would discharge back through the dynamo. This Cut-O 
(s sold by the Electro Importing Co. 

A typical farmhouse, or isolated electric lighting plast 
illustrated by cut Fig. 1, Such a plant as this, of course, dl 
little above the average but does not cost over a few 
dred dollars for the initial installation. The up-keep, !,,_„ 
tenance and safety cannot be estimated in dollars and.ce^l 
A. farm or dwelling equipped with such a plant or a sinuli 
one, can produce electric current at a fraction of the to 
charged by the centra! station companies. 

The principal merits of the electric system for ligtiUt 
the premises, driving small motors and machines, etc, i? J 
comparative safety, cleanliness, and efficiency, as coitiMti 
to any other scheme for accomplishing like results, ^E 
instance, the following features vvill serve to prove the vai 
superiority of the electrical system over acetylene, gas, p 

To begin with an electric incandescent lamp, such as S\ 
carbon or tungsten filament type, consumes no oxygen nti^ 
ever from the atmosphere, and hence it does not devi^ln 
the air, as is the case with any form of oil, wax or gi 
jJluminant. An ordinary gas light consumes as much Qxy( 
ia an hour as six full grown people, and a petroleum 
ierosene oil lamp consumes a much grcattt qaaufttj m 
ame space o£ time. 



I 



Uore fires are caused by the upsetting or explosion ot oit 
Dps annually, than by all other agencies put together, us 
0¥Cd by insurance statistics. So one of the great features 
■c electric plant, is its ability to lower the insurance rates, 
common cause of fire, when the origin is unknown, is of 
arse the now familiar "crossed electric wires." The wires 
the first place, are rubber covered, and rarely ever short 
cuk or come in contact with each other's metal sections, 
is thick enough to hold the electric charge on 
If the wires are properly installed, and rigidly 
place on porcelain insulating cleats or knobs, 
n iron conduit, no trouble whatever will be 
viih the system. 






&'6 



^1^ 



jutjUUl3w1jH(3«c» 



SS|22S?SSSggS 



KSSS 



?££, 



g-'SSS S'^i=tB° 



■-"3 1 



The somewhat elaborate plant shown in the first illustra- 
m, ia made up of a gasoline or kerosene oil engine driving 
(Jynamo. The engine and dynamo in this type of plant 
B usually run during the day, to charge the storage cells 
en at the left of the picture. At the end of the day's 
argc, i. e.p at evening, the dynamo is stopped and the 
rage battery is connected by means of the switchboard 
the light wires or circuits, TU& U^U^* \."t\Mi \a.VfJ(. *.«t 
rgy from the battery M n\gW. ani ^.\\«, aciA i-vj *]2 
iareed again. The phUosopUy ol v'c:\^ s.tV'iiat \?. -ctaJB 
^9 



I cases of privatr hoimes anrl thr like, it is 

sirabli^ 10 have an enijim- o|itraiing durinn the nf){ht oi 
nceount nf noise, attention necessary, etc. However, a wel 

repilatcd system can be run perfei^lly satisfaclorj all Or i 

-art of the night without any undue trouble or annoyance. 

I coinpact engine and dynamo mounted on a single bed' 

gsUie is shown at Pig. 2, The engine is fitted with an cxtr 

wavy fly-wheel to give a steady turning effort or lorin 
Ito drive the dynamo, so that the lights will not flicker. No 
Kvery engine is suited to drive a dynamo for lighting pUf 
^ses. If the speed is not sufliciently steady, then ndUltf 

will the voltage of the dynamo he, and consequently 1' 
Ijights will flicker more or less. Heavy fly-wheels and speoi 
Tgoverning devices on the engines obviate the flickeriogr t.^^^ 
f great extent. If & storage battery is used in conjunctt« 
Jtitli the engine, the lights will not be subject to any flJcket 
png whatever, as the current supplied by the battery i 

^rfeclly steady at all times. Slight irregularities in llu 
>e^d of the engine does not matter so much in this case, SI 

,_le dynamo simply forces current into the battery, much as a 
Jnimp forces water into a reservoir; the battery steadying the 
■ino yoiiage. 




The two simplest systems for lighting incandescent i 

S|-e those employing a dynamo and storage battery separald;, 
"he common circuit for the dynamo system appears at Fig, 3,1 
:he shunt field winding having a variable resistance in seriesjl 
with it, to regulate the voltage apphed at the lamps; but thU 
ft not necessary in small dynamos under 1/6 H. P. In Fig. 4fl 
s shown a storage battery circuit, the 6 cells being connected^ 
a series to give 12 volts (about 2 volts each). 

In the dynamo scheme, the engine or waterwheel r 
^pt constantly going to drive the dynamo, as long a 
fhCs are wanted. With the storage baUery arrawgeiTOcct,'* 
Wc means oi recharging the battery \s necESsaiv- " " 



djrn>n)o is Finptoyed to fnlliU this {tinc(ion. but 1l 
les the batteries are recharged at a nearby pow 
iwncd possibly by a neighbor. _ 

rules regarding tilc siie of charging dy»amos tor 
storage batteries may be of service to llie isolated 
ier. The standard practice in the IJnited States 
Ung and diacharging lead cell storage batteries, with 
Ipltiiric acid for electrolyte, is the 8 hour rate, as 
Ed. This rule works out as follows: H a cell has 
nonnal capacity of 400 ampere hours (being the 
ll.the amperes by the hours), then to discharge it 
kfldard 8 hour rate would mean that 400 divided by 
mpercs for 8 hours would be the normal rate. The 
Ig could bp at the same rate or the equivalent for 
' longer lime.* The voltage of a freshly charged 
^out 2.4 to 2,5 volts. The usual charging voltage 
varies from around 2 volts up to 2.6 volts, at end 
The dynamo voltage must be always slightly 
tbout 10 per cent,) than the storage cell voltage 
s Ihc battery will discharge back through the dyna- 
:ll ia tikely to ruin the battery, To prevent such 
enc^ as this, a reverse current magnetic relay is often 
d between the battery and dynamo, so chat any 
current in the opposite direction to that delivered 
jmaniD will immediately open the circuit, and pro- 
I sets of apparatus. 

useful data is given here relative to the size of 
battery, number of lamps, load allowable, etc.; 



^.m' 






r M|Ual li([ht, he. 



.i^ 


u 


h 


'K 




I 


'l 


11 


III! 


III 


I: 


1*' 


1 


Hi 


yi l^ 


300 B 


l.SOO 


w 


,23 


II 




10 laf 
















tA" li' 






























































wSk i 
















































































2K 57 












so MO 




The methods of wiriiis up & cotiiploie plant, i 
age battery, dynamn and lamps is shown dial 
in Figs. 5 and 6. In Fi^. S is represented o ''' 
plant, without volltneter or ammertr to ' "" 

or ciuantlty, of curreiii passing into < 

while charging or discharging. In Fig. 6 the i 
two "Electro" magnetic vane measuring inst 
baiiety eircuii. which (as they indicaie with C 
direction) will show the voltage and ampen 
battery is being charged or diseharHed, The 
eraJly receives charging current during the I 
charges on the lamp loud at night. 

The sise of ^uire to be used for any given len^ 

and load is best found from the regular fortniU 

Length of run in feet x atTiperea x Z~ 

C. M. ^ - 




■ cfasndeliers for electric lighting, are shown ai Fig 
4r*madcof brass, and make a fine appearance ic 

Hy style shade ran be fUtcd to the chandelier 
J ihc tastes tif the fiiinhaitr. 



tetl 
mally 

eel or 



!"1 



LAMP3 , 



FI6. 4 @ 

for arranging the plants, of whatever eixc i 
lo the builder and operator, 
tamo, to start with, is g^cncrally purchased ready td 
tlocs not pay to build them nowadays. The dynam^ 
located in a. spot free from dampness, or else thor<| 
«IScd over by a woodtn covet. If of greater capacit; 
i P. it should be particularly well s . ' _ 

Mft.foiindBti[in, or tt may be fastened to a wood base 
of Tilled yellow pine. 

plate of most dynamos supply the necessary 
data as to their capacity, 
speed to be driven at, etc." 
The capacity is frequenil; 
given in kilowatt! 
horsepower. To find 
number of watts this 
ing is equivalent to, m 
tiply the K. W. by 1.000 _, 
the H. P. by 746. To fia( 
the K. W. divide the prO' 
duct of the volts multi- 
plied by the amperesi bi 
1,000; and for H, " " 
746. With a given 
ber of watts, the volts are' 
found by dividing the 
watts by the amperes; or 
nperes, divide the total watts by the volts. The 
by a lamp of certain candlepower tC.P.) is 
rom tables in catalogues or textbooks. Hence, 
>ve it is seen that the number of given si 
an be lighted by a certain &ir.e of dynamo 
.__ the total watts capacity of the machine, divided 
bU "watts per lamp. A 110 volt, standard tungsten 

25, 40 or 60 watts, etc., at about 1.2 
!p<iwer as compared to the carbon lamp"; 
W 3.5 watts per candlepower. 
dts arc ihe best for dynamo drives, as 
fttent hook splice gives rise lo irregularity in speed. 
'MAIN 




H«TT 



piaa 



DYNAMO 



ynamo is 
e, divided ffi 

tungsten ^^^M 

3^ 





Fig. -8. 
the desired speed in E.P.M. of ilie 
I example, suppose that 



20-i.i 



pulley rotates on an engine shaft at 1 
R.P.M. and the dynawio is lo he driven al 
2.000 R. P. M.. then what must be the dia- 
meter in inches of the dynamo pulley lo in- 
sure the proper speed? Soluiion; Dia- 
meter of the driving pulley (here 20 inches) 
times its speed (1.500 R.P.M,) equals 
30.000. 30.000 divided by the dynamo speed. 
viz. 2,000, gives 15 inches as the diameter 
of the dynamo pulley. This considers that 
the belt transmission is perfect, but in prac- 
tice it is not. and it is usual lo allow an 
increase iti the calctilated dynamo opeed of 
2 per cent, tor Blippaee- V.vrv frii-h.,,, t,,.it 
slips some, and freijmii ' 
iiuantity of static or h 
"D be provided lo '■ 
acd to a ^ 



I jroximiiy lo ihe moving bell, will dissi| 

iy Etatlc discharges to earth. 

! required width of leather belt tor any i 
I by the following formula; 

192SXH 



W = 



DXN 



, W is the ; 

belt. 



idth i; 



inches of a suitable double leather 



1,925 ia a constant. 

' His the horsepower to be transmitted. 

D is diaincler in inches of larger pulley. 
\ N is the revolutions per minute of larger pulley. 

W» is the width in inches of a single leather belt. 
The distance between the centres of two pulleys connected' 
iQedianically by a belt, should not be less than 3 to 4 times the 
diameter of the larger pulley. Horizontal drives are always 
preferable to vertical drives, as the tension on vertical Systems 
has to be raised to a high degree to keep the slippage down. 
The ideal drive is a well spaced horizontal one, with the loose 
nimring side of the belt on top. For short belt drives, where 
il is not possible to space the individual pulleys at least twice 
L the diameter of the larger pulley apart, then recourse may be 
'had to the idler pulley,-as it is called. An idler pulley drive is 
;Rltistratad in Fig. II. the position of the idler pulley being plainly 
itjdlcated. Its function is to increase the area of pulley face 
covered by the belt, or the arc of belt contact. 




Where the speed of the pnme-niover permits, the modern 
tnetiiod is to direct connect the dynamo, by a metal coupling, 
lo the engine or water-wheel shaft. TViia \a V\vc w " 
Iga/jorf, 3s some power, even thoug^V \ml \Q ^t tw 



T^^ 



Where water power it avtilablc. it behoovti ibe inte 
plant builder lo look il over, and if possible harness it ugtf^ 
ter wheel or turbine. Waier power costs nothing in mn ' 
and the efHciency of the waier turbine ii Teiy | 
somewhere at about 80 per cent, for medium site V 
water. The pressure in pounds per square inch of i.^ 
water ij found by multiplymg the heads in feet bjr s 
lb. per sq. in. per 1 foot of head). 

Windmills are applicable to dynamo drives, 

specially equipped with automatic cut-outs in the Sta^ 
circuit, so that if the mill slows down to a certain it 
also lowers the charging dynamo voltage, the djna 
cut off from the battery. When the mill has agail 
sufficient speed, and the charging dynamo voltapej 
than the battery E. M. F. then the automatic switdf 
circuit with the battery again, etc Another automat., 
is arranged to cut out the dynamo, when the ba.Hl 
received full charge. 

The dynamo itself, if not given proper attention, gives t 
once in a while, and the following are some of the pCulUiB 
watched in operating it: 

The_ commutator is the most difficult part of the dyn 
keep in good condition. The cleaner and {rcer from Mtj 
grease it is kept, the more satisfactory its service 

If the brushes tend to cut or grind, they may t 
proved by soaking in hot parafiine wax ' 

graphite mixture makes the best brush, c 
woven wire center or core are excellent. 
If a dynamo fails lo generate curreni 



OLER PULLEY 




hey r 
A ear^oa)3 
ir those tpiff 

started, iU 
be ^ 

the 

oE roUtloa^ , 

backward. If I 
upon revers- 
ing the direc- 
tion of rota- ' 
tion it itlU I 
refuses to gea- 



shift 



current. I 



forth, If no voltmeter is at hand, a lamp may be connected 
across the terminal posts connecting to the armature brushes. 
1 the above trials have been made without success, 



the r 



> do, i 



t thing 
a direct current through 
cells, or a regular D. C. _.._ 
ture should be disconnected fi 

To lest the field of 
grounded w t n d- 
mgs, use may be 
made of a battery 
and bell or a regu- 
lar testing mag- 
neto bell, such as 
used b y electri- 
cians can be util- 

Care must al- 
ways be observed, 
in small plants pai 
loaded at anvatime. 

machine. 



> charge the field by passing 
rindings from a few battery 
it. In doing: this the arma- 




i^l 



FI&., a 



icularly, that the dynamo is 
any«[ime, as such an occurrence is aim' 
)Ut tbe windings, necessitating a rewinding o^ 
To this end, a reliable voltmeter and ammeQ 
should always be in circuit lo sliow fhe toVaV 103.4 ow -^^^ 
dynamo at any instant. The proper cuirenl \u a.tn^^T«& C3| 



46 




bavcn Imraepower ami voltage is readily figured out as 
led previously. 

'^lly all of the best automabiles and motor boats to-daj 
: sA with electric lights. An outfit composed of Electro 
Co.'s goods is shown diagram matically at Fig. 12, The 
>.. .. ;ji>uld deliver 8 volts or more, for recharging a 6 volt 

^•^^:^^i. Lattery, and their No. 165 generator is a fine machine 
^or auto and motor boat lighting plants. It is waterproof and 
J^ery rugged. Such an outfit should comprise the dynamo, an 
jkoBomatic cut-out at $9.00; a No. 5SS 6 volt. 60 A. M. storage 
KMtiery, and the desired 6 volt tungsten lamps. This outfit 
Ktill ignite the engine by the jump spark cmls, and also furnish 

Ctveral lights siratiltaneously. An 80 A. H. battery at $12«1 is 
(tea desirable for auto lighting. 



LESSON NO. 6. 

teBLECTRICAL WIRES AND THEIR CALCULATIONS. 

•j^W'^HE metallic conductors or wires which are employed 

■ I to convey the electric current for various ptirposes 

I are usually of copper. In some cases, as in telegraph 

and telephone line work, iron wires are used, iron 

rirc having about seven times the resistance of copper wre 

il shiiilar diameter and length. 

la all practical calculations for electrical wiring, etc., the 
(Toss-sectional "area of the wire is spoken of in circular mils, 
and sometimes in square tnils; one mil being equivalent to one 
one-thou&andth of an inch. A circular mil is the area of a 
drcle of 1 mil or 1-lOOOth of an inch in diameter, or also it 
eijuala the diameter in mils squared. This follows from the 
well known rule, that the area of a. circle in circular inches is 
Found by squaring the diameter in inches, or d'. The area in 
square mils, is evolved by the usual circle formula; d' x .7854 
= area; or area in square mils, of wire, equals diameter in 
kdls. multiplied by itself, and then by the constant .7854. The 
km of >■ wire in square inches is of course found by the rule — 
dtltiieter in inches squared, times .7854. 

All wires usually conform to some standard gauge or series 
of arititrary nunfbers. The e^uge sitandardiied and used en- 
lirriy in electrical work in fhe United States, is that developed 
' V ttiC Brown & Sharpe Mfg. Co., and known as the American 
win Gauge, (A, W. G.) or simply the Brown &. Sharpe 
"" (B. & S. G.>. The various gauges in use and their 

given below: 




Brown & Sharpe's Gauge. 
3. & S. Gauge is standard for copper wire and is under- 

. > apply to all cases where size of copper wire is men- 

" tioned in any wire gauge number. 

By referring to the table it will be seen that in the B. ft S. 
Gauge, to all practical purposes, the area in circular mils, is 
doubled for every third size heavier, by gauge number, and 
halved for every third size lighter, by gauge number. 

Every tenth size heavier by gauge tiumber has ten times the 
area in circular mils. 

Every No. 10 B. & S. Gauge wire has an area of approxi- 
mately 10,000 circular mils, and frfm this base the other sizes 
can be figured, if a table should not be at hand. 

Classification of Gauges. 

addition to the confusion c.iused by a multiplicity of wire 
,. several of them are known by various names, 
example: 

& Sharpe (B. & S.) = Amencw \J\te. C>!».«i "v^- 

^^ 




9BI^ 



N«w British Standard (N. B. S.) = British Imperkt, 
tish Le^t Standard and Standard Wire Gauge and is 
abbreviated by S. W. G. arwi L W. G. 




Pig. 1. 

Birniing'ham Gauge CB. W. G.) = Stubs. Old EngUdi-'; 
dard and Iron Wire Gauge. , 

Roebling = Washburn Moen, American Steel & Wife' 
Iron Wire Gauge. 

London = Old English (Not Old English Standard).. 

As a further complication: 

Birmingham or Stwbs' Iron Wire Gauge is not the s 
Stubs' Steel Wire Gauge. 



Table No. 1. 









■s 


fS 














r 


^ 


M 








































































1 




r. 


ir,i 
































































































1 


« 


^ 


■w 


l 


!^» 


ffii 


' 


'! 


^ 


^ 






^ 


•M 


■££ 


ri- 


S 


^•^ 



s 



±1EM 






ai'i'.ssSil'fS 



General Uses of Various Gauges. 

B. & S. G.— All forms of round wires used for electrical 

ductors, Sheet Copper, Brass and Gemnaw SiWer. 

U. S. S. M. G.— Sheet iron and si«e\. l-tKaWitij^i^ 

Congress, March 3, 1S93. ■ 



Table No. 2. 

TABLI~{tr CAHRVINO CAPACITY ST 
Maw li k Ubie ahDWlDC lbs sjlowable unrlcg ue 

Nuasen coveoed wires. 




W. G.— Galvanized iron wire. Norway iron wire. 

Atnerican Screw Co.'s Wire Gauge. — Numbered size of ma- 

Ine and wood screws, particularly up to No. 14 (2421 inch); 

Stub's Steel Wire Gauge.— Drill rod. 

iRoebling & Trenton.— Iron and steel wire. Telephone and 
legraph wire. 

1. S.— Hard drawn copper. Telephone and telegraph wire, 

London Gaug-c.— Brass wire. 

The Brown & Sharpe wire gauge, is given below, see table 

X I, The areas in circular and square mils are both given. 

iO the resistance in ohms per 1,000 feet of len^h, etc This 
instance is in International ohms, not in B A units. , 

Table No, 3, 

1ENT REQUIRED TO FUSE WIRES OF COI>Pen, QCRMAN BILVM 



;The table of carrying capacity of various wires, table No. 2, 
that recommended by the Fire Underwriters, whose rules 
lit be 'Strictly followed for all electrical wiring and inslalla- 

Sonje other useful wire data is also appended her«, table No. 
_ including a table of the current required to fuse wires of 
fgioas sizes and kinds. A \.ab\e oi er\mvA\fo!i. Nrat^. X:SS« 
^ 4, which shows how matty amaV\M wvies Wi w^wtJi^jc*-. ' 
■ ore large one. The otticf da\a vs lot awwavn^M.'w 'hv 




Obviously it would be quile impossible for any one alloy 6 
possess all the properties died, but a number of alloys ar 
manufactured each of which possesses certain charac^eristi 
prdpi^ks rendering each eapeciaWy ada^taWt iot cm\.^i\ 'i 



PJMir silver wire is drawn from an alloy of copper, nickel 
Vnc and tiie grade most uwd in electrical work is the one 
Hi as 18 per cent, German silver and which conUins ap- 
mately 18 per cent, of nickel, while its resistance is ap- 
imately 13 times that of copper. A 30 per cent. Gennaa 
r wire contains 30 per cent. o( nickel and its resistance is 
it 28 limes that of copper. This wire is not recommended 
a.it is- subjected lo repeated heating pad cooling,, as it 
Ties extremely brittle. 

the trade name of a wire of a copper and nickel 
. and contains no zinc. Its specific resistance is 28 times 
of copper and its temperature coefficient is practically nil. 
wires does not become brittle with repeated beating and 
Og and is absolutely non-corrosive ; wire made of this alloy 
rly med in the construction of measuring instruments, 
wee units, motor starters, etc. U can be procured in 
ribbon or wire, and the latter may be had either with 
cotton or silk insulation. ' . 

ilher resistance wire that has a resistance of 50 times thall 
Jper goes by the trade name of Climax, and a general idel 
■at this means may be understood when it is stated thai 
iry iron wire has but 7 to 8 times the resistance of a 
r wire of the same diameter. Unlike German silver wire.i 
R-wiivwill not become brittle wittt repeated heating andl 
_.g and its high specific resistance renders :t an economical 
titute. It is largely used for rheostats, resistance units, art 
potentiometers tor wireless receptors, etc. 




nc.z 

new wire known as Ntchrome, has several important fea- 

ilKbich makes it distinctive and highly efficient for cice- 
ly beated apparatus and resistance elements where severe 
Jt]ons are to be considered. Its specific resistance is about 
per cent higher than any other alloy. Nichrome withstands 
— '":ly high temperature without oxidization, is practically 
rosiwe and will not become brittle with repeated heal- 
and cooling. It may be obtained in either riUion or wire 

wire manufactured espedally for Dse in measuring instiu- 
te and standard resistance and therefore extremely suitable 

wireless apparatus is known as Manganim. An important 
are is its exceptionally small temperature coefficient, where 
' a difference of from 10 to 30 degrees centigrade need be 
.ddered, the change in resistance is so small it can be neg- 
led. Cut Fig. 1 shows the relative ' ' ' ' 

iven 



for a specific case is 



Uiere R is the required rea iatance In ^ftma. 
is the drop in volts requifd ^^»^-i 



And C is the cur 

For dectrical circ 

the required load i 

knmwn as the drop __. 

systems, is 3 to 5 per 



on 110 volt systems, etc. 



it to be passed. 

s the wires are alwayi desisnecl to can 
amperes or watts, with s cecUin In 
volts. The usual drop for low voltai 
""' of the line voliage or about 3 vol 




u 



u 



The simplest method of finding the size of wire required U 

I certain length of drcuit, to carry a given load in an 

with a known drop in volts, is frum Ohm's law:— 



Where R represents the resistance in ohm.s ot the total 
fn the circuit. 

E is the drop in v&lts allowable on the circuit, usually 3 In 
volts on 110 volt systems. 
C is the current in amperes to be passed over the cirouit 
^Findinff the resistance of the total wire (both »4e^ in 
drcuit, the si^e of wire B. 8; S. Gaus'e, having thii "reaistl 
per required Iwigth in feet, is ca5ily found. 
21.6 X d X C 
C M = ; 




21.6 X d X c 


C. M. 

V 


Cx2d 

V 



2d = 

C X K 
= di^nce of load, or lenph of circuit ooe way to cen- 
ls_o( distribution id feet. 

urrent required in amperes. ^ 

r = volts drop allowed. 

"■' r useful forms of the above expression are as foUowa: 
re K = resistance in ohnts per foot of wire to be lued. 

amount of current required for various classes of load, 

I dependent upon the watts consumed by the apparatus. A 

■^ watt motor on 110 volts will consume 550 divided by 110 

amperes. Carbon filament lamps, take about .5 amp«e 

le 16 candlepower unit, and one ampere for a 32 candle- 

■ lamp. Tungsten or Gem metallized fiiamwil lamps take 

wpttage designated on their label, as 40 watts, etc, and thS» 

led by the voltage of the circuit gives the amperes of euf- 

oonsuraed by them. 

'here a bank of lamps are connected onto the circuit in 
biJtiple the total current taken will be the number of lamps, 
!S the current per lamp. As an example:— If 8-16 candlc- 
■er carbon filament lamps were connected on multiple, the 
■ent taken by them would be 8 times .5 amperes or 4 
leres. 8-32 candlepower lamps on multiple would require 8 




riG.S 

1 ampere or 8 amperes. The load current for a bank of 

;n lamps may be ascertained by finding the total watts 

med by the bank, and then dividing this value 1^ the volt- 

' the system. 

nen installing wires for D. C. motors, an extra allowiance 

; be made for the starting current, which is somewhat 

ter than the normal running current It is usual to cal- 

;e on 25 per cent, greater current than that normally taken 

' or, but 50 per cent, over allowance is better. The 

r running current consumed by a motor is not only that 

I by the number of horsepower mechanical output, but 

lus that amount lost in the motor, due to its transform- 

: electrical into mechanical energy. This efificiency of 

I varies from 70 per cent, up to 98 per cent, in the 



s of 1 



: D. C. r 






K formula may be dedacod lor the purpose of fintHng tin tt 
uJRie siie of conductors ior atiy siie D. C motor, wmdi tii.. 
into consideration the 25 per cent, excess currenl required Ij 
tile Fire Underwriters' Rules ^— 

(P X 746 X L X 22 X 125) 

A = . in C M. 

(E X c X Efficiency) 

In which :— P is the rating of the motor in mechanical H. I 

L is the distance in feet to the motor. 

E is the impressed voltage of the circuit. 

And e the allowable drop in votts in the circuit; (varying from 
4 to 8 volts.) 

When the proper size of wire has been found from the above 
or other rule, the table of carrying capacities of rubber cov- 
ered wires must be consulted, and if the wire calculated )u« 
to carry more current than that indicated in ihe Underwriters' 
table, then the size of wire recommended by them must be 
employed even though it is larger, and more expensive than 
fhe one calculated. (See tables No. 1 and 2.) 

Ip alternating current systems, as single phase two \ 
where the load is only incandescent lamps, the rules and _ 
mula employed above for D. C. circuits can he applied; ■<» 
inductive skin, and other effects being negligible for onriayW 
lamp circuits not exceeding 500 to 1,000 feet in length. C^ 
important item, in the installation of A. C. wires must not 
oVerltioked, and that is; that the two wires composing ^'^ 
cult must both be placed in the same iron pipe or feoittft 
otherwise serious inductive effects, and consequent he^til 
will be set up. For this reason it is advisable to always mf " 
the two wires of a circuit in the same iron conduit, even ._ 
is to be utilized for D. C. as later it may be desired to ch&nfj 
th ft 875 tern to A. C. and it can then be readily done, wtthttT 
any changes in the wiring. i _^ 

Except in fixture wiring, (where No. 16 or 18 runber C« 
ered fixture wire may be used), no smaller wire is (o be W 
stalled than No. 14 B, & S. This may be asbestos 
or weatherproof rubber covered, where the wires are 
to view and rigidly supported on porcelain knobs c 
spaced every 4^ feet. Where the wires are to be plaScd', 
iron pipe, flexible circular loom, or in other concealed 'lot 
lions, it must be rubber covered, double braid. Single,^ 
rabber covered wire is permissible tor exposed leork, wherJ 
wires arc in view at all parts of the circuit. 

"The so-called B X cable, is a very good comblnatior . 

ible steel conduit and impregnated wires, which is extcnsfrd 
applied. It comes in any desired size, and has only to be ' 
ened in place, to make the finished job. 

For most wiring, it is difficult to install solid copper C. 
ductors having greater area than No. 4 B. & S. rubber cove« 
and so stranded cables, built up of numerous small co] 
wires, so as to be more flexible, are employed. The eqtiiva., 
area, of a stranded cable of any size, is found by multt^bn 
the total number of wires in it, by the area in circular mifit 
one of the individual wires, which gives the equivalent arci»Vjl 
C. M. Cables or conductors of greater area than No. Mr 

B. & S. gauge are always rated in C M., lhus:-^,000,8 

C. M, cable; 4,500,000 C. M. cable, etc. 
In three wire D. C. systems it is common to divide b, 

lamp load between the centre or neutral ^ne, and thent 
outside wires. Motors are invariably, except those. s-*~ 
than one-quarter horsepower, connected across the < 
wires, The voltages of the three wire D. C. system are gepd 
ally 110 volts between either outside wire a;id the neutrsO, vi^ 
220 volts, (for motors), between the two outside wires. TI' 
saves considerable copper, as the current required by mot< 
oa 220 volts is only one-half that required on 110 voltB, " 
twice the drop in volts is permissible ow 220 voVta, as 
« d to thai on no volt circuits. 



f^r-^w 



■^^ 



r incandescent lamp loads on the three wire system^ .~, 

, be considered that the lamps are «venly balanced on the 

I sides of the system, in which case no current would 

tree the neutral or centre wire at all. In figuring out the 

s, etc., it is seen that wi(h the lamps, two in series, on 22ft 

I, the current will be but one-half that, if the lamps were 

n multiple, on 110 volts. In other words, the current to be. 

d on, IS but one-hatf the regular 110 volt rating, and the 

t voltage is doubled, with twice the drop permissible on 

jlts. The outside wires are calculated for the raotor loaid 

_ It in the usual manner, at 220 volts rating. The neutiul 

; is always made equal to the outside wires, in siie, in 

i commeraal installations. Acting on the possibility, how- 

', that the system will never become totally unbalanced, the 

'— i wire is often made smaller than the outside wires. If 

__. J should blow in one of the outer feed wires, however, 

J resulting load on one side of the system, would have M 

.; carried by the outside wire and the neutral ; and hence it 

i_ always advisable to make it at least as large as the outer 

t three wi^e Edison system is utilised with various com- 
is of power generators and balancers. The original ar- 
ent was that making use of two dynamos of 110 volts, 
ed in series. The neutral wire was connected between 

_s illustrated by the diagram, Fig. 2, M, being a motor 

UOIS the outside leads; L, the Iamp_ load, balanced on t^e 
3 ddes of the system as near as possible; G, and G2, tiie two 
1 volt generators. 

Another development of the three wire scheme is that at Fig. 

1 where a storage battery of voltage equivalent to that across 

! two outer wires, is floated across the generator, and bal- 

9 the load requirements of the two halves of the divided 

m supplying lamps. 

___; latest way of arranging the three wire system, where it 

B desirable to have 110 volts for a few lamps, and the main 

t supplies 220 volts, D. C. is the wolor bahncer set, xlias- 

d by Fig. 4. The regular 220 volt motor load is taken 

_..i the leads of the generator, G. The two small motors 

[ M, connected rigidly to the same shaft, operate alternately 

1 a ]notor and a generator as the lamp load increases and 

screascs on either side of the three wire rircuit. When tiie 

nd on one side becomes too heavy the motor on that side acts 

1 generator, helping to carry the load, and the other motor 

„ the opposite underloaded side of the system, acts as a raotor 

t> drive the generator on the other end of its shaft, and vice 

na, as the load fluctuates. 

Pig. 5, gSves a working diagram of a commercial balancer set, 

Eaduding the circuit breaker, C. B. ; field regulating rlieostat, 

\ R.; ammeter, A. M.; generator (220 volt D. C), G.; shunt 

Wd winding, S. P.; compound field winding, C. F.; armatures, 

1 and starting rheostat, S, R. 

Tien the system is perfectly balanced, no current passes 

flgh the neutral wire, tlie fcalancer set running idle at a 

i sufficient for each armature to generate a counter E.M.F. 

tage) very nearly equal to one-half the voltage across the 

ide wires. As an exam.ple, if the outside wire voltage is 

~Ti then if the E. M. P.: on one side of the tiiree wire 

should drop below 109 volts for instance, the armature 

machine on that side of the system, would act as a gcn- 

.- to maintain the voltage, while the rise of pressure on 

oflier side of the system, would cause the armature con- 

;ted to it, to operate as a motor, and drive its (now gen- 

Ltor) dement at nearly constant speed. 

ia well to have each field of the maehines of the balancer 

lipped with a few series fieM convolutions, and so con- 

that, when either machine operates as a generator its 

_ cumulatively compounded, an»i when running as a motor, 

differentially compounded. By t\\\s Tivewv^ ftit -io\'iwt\^\ 

jeocrator will be slightly raiBed. oVto^ \.<i ftit % " 

strength and also to the greater s^eeA cil wve w 




Its wtalceocil fidA Wbea 

"i<T "re tenced cussluivc and 
il« another, they are rrfciTed W u 4aM* 
lo &, Uotors and lypataoi.) 

Slccnacal Uaitm. 

Tbe dcdiical nchs are as fc^cnrs: 

Vo[t — Unit of niotJTe force. Force r e pair ed to send one 
Ere of ccrreni tfarMigh ooe ofam ot rcnsmice- 

Ohm — Unit of teaiitatne. Tbe rc^staaee offered to die j 
ige of one ampere, vlieci iapeBed by oik volt. 

Ampere — Unit of ctureoL Tfie cnrrait wlad one volt 

«d ibrongta a resisUncc ot ooe obm. 

Coulomb — Unit of qnasthjr. Qsanlitr of current whidi Ibk 

iHed hj one volt wouM pass throngli one ofam in ooe i 

F4rad — Unit of «apadty. A condiKtor or coodeitser 
tin hold one n>ulrmil) under the presnrc of oae *o4t. 
' Joote — Unit of work. Th« wMk dctie by one 'wact in one 

HOfMl 

Wall — Oirii of energy, and is the product ot the ampere 
N}U. That is, one ampere of ctirrect flo wi ng imder a 
H one volt gfves one watt of energy- 
One Electrical Horse Power is equal to 746 watts. 
One Kilowatt is equal to 1000 watts- 
Ohm's Law connects the thrre onits. volt, ohm and 
cnrnitt in any drcnit is directly proparttona! 



trOTnotiYe for 



, and inversdy propiorrior 



drcuit an electromotive force of one voh producei - 
current of one ampere. 
OWs law Is: 

Electromotive force in votts 
Current in anipefes= 



AtAreviated i 



Reu stance in ohms 
: C, current; E, volts; R, resistance 



=12 amperes. 



(2.) A dynamo to send a current of 2 amperes through a f 
jpstantt of 2S ohms must have an electromotive force of'l 

*eki. 

" -2x25=50 volts. 

a drcuit when an electromotive ot 1 

of 10 amperes through it will b« 80 6ha 



To find tlie watts c 



800 
R=— =80 ohm». 
10 

,„ „„^ „,., .. ^cniBUried in a given electrical drcuit, 

As • 1«mp, multiply the volts by the amperes. 

To find the volu, divide the watts by the amperes. 
To find (he amperes, divide the wiatts by the vohs. 
To find the electrical horsepower required by a lamp, dividi 
■Ihe watts of the lamp by 746. 

Tn find the number of lamps that can he auppUed by tmi 
elceirical horsepower of energy, divide 746 by the watts of thi 

NJTlLfirit ihii cleclricfll horsepower 

•ef Ump by the number of bmps and divide^ 
To fnd the medianical horsepower r-~ ■■* 
rT<iaiTed electrical horsepower, divide 





i the volts wihen the amperes and watts are known, 
the amperes by the oihms. 

i the resistance in ohms, when the volts and amperes 
n, divide the volts by the amperes. 

Required to Fuse Wires of Copper, German Silver 

and Iron. i 

ited from the formtvla ad 3-2 = Q where "a? b a. 
depending on the nature of the wire. For copper, a = 
irman silver = 5230, and iron == 3148. (Tfais fonasila 
W. H. Preece. F. R. S.) 



Copper 


German Silver 


Irofl 


333! Amp: 


169. Amp. 


101. 


' 284. 


146. 


86. 


235. 


1207 


712 


■20O. 


102.6 


63. 


166. 


852 


502 


I 139. 


712 


42.1 


^ 117.; 


60. 


3S.S 


^ 99. 


5a4 


32.6 


82.8 


42.5 


25.1 


667 


342 


202 


58J 


29.9 


177 


49J 


25J 


14.9 


412 


21.1 


12.5 


34.5 


177 


10.9 


28:9 


14.8 


8.76 


24.6 


12.6 


7.46 


20.6 


10.6 


622 


177 


9.1 


5:36 


147 


7.5 


4.45 


12.5 


6.41 


3.79 


10.25 


5.26 


3.11 

# 
r • 


a75 


4.49 


2.65 


7.26 


373 


22 


6.19 


3.18 


1.88 


5.12 


2.64 


1.SS 


4.37 


2.24 


1.33 


3.62 


1.86 


1.09 


3.08 


1.58 


.93 


2.55 


1.31 


77 


2.20 


1.13 


jS7 


1.86 


.95 


S6 



ASOpm 



vt 




IGinineten 
MilHmeters 
Meters 
Meters 
Kilometers 
Kilometers 
'Sqaare cen timet erf 
! centimeters, 



pectares 

jiitMC centimeters , 
Cubic 

Cubic meters. 
Cubic meters. 
jbWc meters 
Bters 



Slog's per sq. centim 

"'log's per sq. 

Slog ram per cubic r 
Eilogratn per cubic r 
KEctric tons (1,000 kilog's)...X 
Metric I 



tSBSON No. 7. 

TELEGRAPHS AND TELEPHONES. 

cteclrii: telegraph was the forerunner of the tele- 

phoDC, and so we may naturally take up the study of 

its operation first. S. F. B. Morse of Che UoUed 

Stales, was the first one to perfect an electro-inag- 

>h signalling instrument, which also included a 

emp1«ying a moving paper tape, upon which the 



LINE 




gifrts ind dashes were recorded. The tap* register is 
jti in many cases, but generally the familiar "rounder," 
f>ff the dots and dashes, signified by the short and long 

of the current through the sounder. 
Tkt simplest telegraph set for experimental use is easily 

of two ordinary "buzzers," 'two push buttons, and a 

f ft* illustrated by Fig. t. 
n Ae diagram shown two lines of copper or other wire 

S resented, but one of these may be substituted by the 
I j|he latter being denoted as optional by the dotted 
"foing to G. G. The operator at either end of the line 
At push btit- 



Of a dash. Tiie 
1 letters of the 

t are made up 
ufcrent comiMna- 

, of dots and 

'Cities as exhibited 

Wow, and make up 

■•ifom" code. In 

*liat is known as the 

*rireless telegraphy, there 

(he Morse, U. S. Navy, a 

Continental Code lies in the fact that . . 

Bie letters or figures, as in ihe Morse Code. 

The average speed of sending and 
neisBges varies from IS to 50 words pe 
to the condition of Ihe line, and the adi 
I wireless work the speed is u. 
I expert operators. 




. _ three codes 

id Continental. The advantage of the 
spaces in 



telegraph 

, iccordiag 

5 of the oper- 



pbainper (he speed of 
irirtf tines, which experie 
tttier, causing the line a 



here, 



ally 40 words per 
ad weather condi- 



■r . 


The sbntile 




er's lelcKTaph 




^^ ^^^L depicted at 1 




^^^^^^^snd comprises 


Im^ mb*^ \ 


^^^^r ohm sounder ai 




V Two cells of d 




1 tery will work t 




i over lines Dot ( 
ing 50 fe«t in 




S-Caudor.l Kej 


It can be bs 


longer lines b^ em- 


imi 


ploying a relay in coo- 




nection with it, or its 


B^^,^__^m 


magnet coils may be 1 








sistance, allowing it to M 


WK^^KBk 


vfork with less cur- ^ 




rent A common re- ^ 




si stance for sounders 




on larger lines is 20 


Fig. 3. 


ohma. 




A cut of a standard key is shown by Fig. 3, tlie 4 


one being a strap key adapted for light wgrk, sncq 


buzzer circuit. Several forms of relays are seen at fl 


5 and 6. At Fig, 4 is the 


Gernsback relay. Figs. Si 


show the make-up of a polarized relay. These rel^yll 


with the current coming 


in oifc certain direction 


Reverse current dots not 


ffeet them. Hence they al 


ized on iJupIex and other 


elegraph work, where moi 


two signals are to be sen 


over a line simultaneouil; 


For ordinary lines no 


t over 20 miles long, a I! 


relay is usually employed. 


Higher resistance relays a 


(or long distance circuits. 






F«r 1 




ginner, 1 




practice , 




by tead 




? an expei 




a ator. V, 




■ ^ this IS a 




■_ S sible, ai 




■^^fl_ maae 


1 ^^^^^^B 


^ JS^^ instrume 


^^^^L ^^^^^^fefii 


f^^^^^^ regulaie 




^^^ any 




speed. 


^^^B 


"Omnig 




i:nt of V 


^^^Hfewn at Fig. Of, 






^^^^nrhc battery 




^^^^■eneratly used J 




^^BW all commer- M 




^^^Hjial telegraph W 




^^^^vice is the 1 




^^'"^i'-Z »\ 


^^M\Jlw fE 


f "Blue Vitriol" A1 




1 battery. Cop- JVU 




1 per Sulpbate ^^H 




1 crystals are J^^| 




1 placed in water i^^H 




k to m a k e the ^H 




B e/cctroJyte, ^ 




■ While a zinc 




V and copper elec- 


jll^g 




h!rioraie» very rapidly. Fdr intermittent tcrvice, »nv 
««r be used. The Edison or Gordon primary 'cell 
IM for beavy duty on dosr^d drcuit, and give good 
ictilu standing idle or not. The various characteristics 
nity and otber cells is thorouglily discussed is tlie 
I BaHerie;. A cut of a dry cell and a Gordon 300 
DC primary cell are shown at Fig. 8. 
W words will now be devoted lo the connecting up 
ivmunents on several lines. In Fig. 9, is shown the 
S&A for a learner's set, consisting of Sounder. S.D. 
*vd Battery, B. In Fi^. 10, is seen the hook-up (or 
ie liat (two wires) wnh two sets of instruments, 
.'iocal battery at each end of the line. A Rroimded 
IW fighlning arresters complete is depicted at Figi 
EiX is fhc lighlnfng arresters, R tJie hi^h resistance 
, |th« sounders, K, the key, L.B., the local battery for 
tll«-«OUnders; M.B., the main battery ioT working 
■er the line, and G, the ground connection. As 
_,.., rhe depressing of the Key K, at either ead of 
■it, sends battery current through the opposite star 
Jay magnet eoils. .This causes the relay armature 
tawasd Ihe magnet poles, and in so doing it closes 
ita-ct for the local battery circuit, through the 

s. 

mercial operation now, 
. pne message is seut 

( ^four in each direc- 

«jglit simultaneously : 

nns Viixst is known as 

adruplex," or simply 
■■' System. The quad- 
em -is quite compli- 

. involves the use of loading or balancing i 

atiu. Maver'a Bock on American Telegraph Practice. 




OmnlErnpli iritli SpriaB 



ovBf a wire several haadTCil inilts ujng. The 7"jl_ 
a perforated paper upc, prepared in a maihlnel 
a typcvrriicr, which is then placed in the 




itor, ihe Fi 
tuee Medal 
Submarine te._ 
is a large brandi 
bii;ine:i5 and nuk- 
of numerous cablet 
in the ocean, an " 
jecting around _ 
world now. TlMli 
will probably be 4 
\n ed, now that thc 
less system can so : 
ily bridge distances of several thousand miles. A refledJm 
vanometer or Kelvin Syphon recorder is employed lof 
marine signalling. The current r — ■--■■ '- ' 
weak, and also greatly re- 



rig. & 



S& 



tarded owing i_ .. _ .__„.. 
capacity of the submerged 
cahle. Cable messages are 
usually transmitted at speeds 
not exceeding 12 words per 

The Telephone is one of f 

the most useful inventions 

of mankind, many times I ^i 

more so than the telegraph, I a 

perhaps, but both fill thdr fiq 

particular functions well. 

The first successful speaking telephone was pait 
by Alexander Graham Bell, and was exhibited at ttN^i 
tennial Exposition held at Philadelphia in 1876. Ii w 
weak and puny affair, that first telephone, but it talked 
now we would not know what to do without IL Itf 
would paralyze the world's business, at least in euA h 
of activity as New York or London, where buildlaC 
Stories high are buikt. 

The various parts going 
phone, are shown at Fig. !Z. 
receiver, battery, anil hook- 



1 make up the simplettj 




i( of a "Telimphono" Is seen at Fig. 13, This Ins 
mem will iilk satisfactorily on circuits not over 4000 
long, and sells at a very reasonable price. 

Hefcrring to Fig. 12 again, we will now discuss the i 

s parts of a telephone and theit individual functions. 

Tilt battery is usually of dry cells, two being gener 

aaflkient, and supplies current (o^he seL The transmi 

ial}y made up of two ^4H^Bbc^ between whiif 




fiS 




aoM the iron diaphragm to vibrate, the attached 
£ also vibrates, which causes the contziGt between 
n granules and bolh discs to vary, and the rcsist- 
wise varies according to the strength of the air 
Binally produced. 

receiver has a similar soft iron diaphragm, placed 
^nnanent magnet, upon the end of which is wound 
! insulated copper wire. The irariations of the 
MlMth in the circuil, created by the transmitter. 
la Ine receiver, and causes corresponding varying 
gnelic forces to act upon the soft iron diaphragm, 
a ihort distance away from the pole face of the 

letloin of the various parts in reproducing articulate 
readily perceived by looking at Fig. H, 
I seen that two similar eleclromagnets and sets of 
iragiss are connected together hy copper wires. If 
1b projected into one of the receivers, the slight 
t of the diaphragm at that particular insiniment will 
Itnts to be generated in the coil on the end of the 



,11 surge out 



nnaneot magnet, and thi 
line wires, and into the i 

if the line. When 
ing currents pass 
e coil of the sec- 
iver, they create 
in the strength of 
etic flux affecting 
■agm, _and hence 
wm its attracted 
A gimultati eou sly , 
E to air currents, 
to, and thus 
Ig l"he voice at the 

• end of tlie line. 

,oi^ distances two good telep 
series may be used for a telephi 
a [ransmitter as well. This was the method fol- 
tlie early instrument, there having been no trans* 
"mil Berliner perfected his type. The trouble 




iver acting as a transmitter, is that its . 

M sufficiently distinct or pronounced for the voice 
itt actuating it, and heqce the decided change in 

t>t the carbon transmitter for changing .yolce 

proved a boon. 

set shown at Fig, 12, no induction coil is sKovJ'n. 
jnntnt being adapted to short Wnt »ctn'\«, XkA 
Sia^fc apparatus the talking diatances have idcV^ 



.., P.H. Wheft this button ia io the normal position, it 
sses the bell circuit, as shown; proyiding the receiver is on 
me hook-switch, which depresses it against the ringing con- 
Tt spring. While talking- the ringing circuit is open, the 
^olc-switch making contact against the two tipper springs 
Kuid 4, seen ia tlie diagram. 

■For a two party line. It is only necessary to string a. couple 
T, insulated wires, such as bell wires, and connect their 
jmiinalG to the line posts of the instruments 1 L, and 2 L, 
Espectively. 
K hook-up for a central battery Bet of two telephones, 
ich has many good points to commend it, is depicted at 
[. 16, In the set, which is not intended for lines over 
nile long, no induction coil is used. The central battery, 
ced at either station, C. B., supplies energy for talking 
I'Well as ringing from either station. To ring the opposite 
Btion, the ringing key. R. K., is depressed while the re- 
iver is on the hook. This telephone is a series instrument, 
of standard manufacture. C. K. represent resistance 

.\)r line wires, No. 18 to 20 B. & S. gauge copper wire is 
lerally employed. Bell wire is very good, if ktpt separated 
the run; or if more than two wires arc run. a good 
:onsists in making up a cable of them, and taping the 
bunch together, by wrapping around with black friction 
letting it overlap about half of its width. This cable 
iily and neatly run, and makes a very fair job. 

telephones are those installed in fac- 
other places, which are provided 
switch to allow of talking to any indi- 
the system. Fig. 17 illustrates a four 
'eating set, either one of the three in- 
to ring up any other instrument. The 
for this system ' — '"'" " " 






i connected, the 




^mtnts bei 

_6 'than th. 
3 wire being called the 
ramon return wire, as 
5 telephones have 
E their leads con- 
«0 it. This set is 
in-interfering, and 
f party can interrupt 
nher, or Ksten in. 
systems of this 
are so arranged, 
interference be- 

the various parties 

t imlosGtble. 

'" runnang telephone 

Its, it should be w 

1 that each hne is of equal length, or else the apadty of 
) lines wdll bci unequal and give rise to imsatis factory 
Electro- magnet windings, such &B bell magnets, or the 
like should be 
kept out of the 
talking circuits. 
Long circuits 
returning b y 
the earth or 
groundt should 
be avoided in 
telephone eerv- 
iro> as this Cre- 

©F, B, I s the instruments. 

._. eedinfir one-half raile, ground returns Me-swversiW'j su.'si^'v'a.'Ajsvi. 
In large telephone exchanges, ser\ing sutV^ t\\:\c^ ^a '^i^ 
"t w Chicago, the battery powtt ioT a.\\ \,a.Vii;vo.s aN- v 




exchange or subscribet't tnatrumenl is centralized at the ' 
change. A storage battery of 24 volts poientml tiippliea ' 
talking current. Ringing current is usually alternating 
pupating at about 70 volts potential. Calling the open 
is done by simply removing ihe receiver from the liool 
which act releases the hook, and this spriaging tq 
closes the circuit to the exchange. In this circuit it t, t 
tive relay, which closes a local circuit through a 24 \€&t 
OR the switch-board before the operator. When lli« 
lights up. the operator plugs into the corresponding- c. __ 
jack, and ascertains what number is wanted. Having low 
out the desired number, the desired party is rung up 1 
pressing a ringing key, and when they respond, the operali 
connects the two parties together by means of flexible Con 
and jack plugs. 

The automatic switch-board is coming ahead rapidly,*! 
has a host of commendable features. No manual 
are employed, except for effecting long distance call 
there arc no central girls, there can be no interference, 
hence many people will welcome the automatic switch-b 
Chjcago, 111., and l>os Angeles, Cal., have two of tie 
est automatic switch-board exchanges extant. Numi 
other smaller cities are now equipped w" 
changes, having no operators. 




The average time consumed in making 
tween two parties in modern telephone pr; 
4 to 12 seconds. 

The telephone has "grown to he one of the most bi^ 
developed if not the most highly developed branch of afc 
trical engineering to-day. It employs over 200,000 pcopl?" 
the United States alone. 

Telephone engineering is a paying and highly intertt 
ing profession. There are thousands of problems Ca ' 
solved yet by the coming generation. 



LESSON NO. B. 
DYNAMOS AND MOTORS. 

DYNAMOS and Motors are electrical machinea en 
ployed for the conversion of electrical energy int 
mechanical energy or vice versa. They depend^i 
'their operation upon the ccpulsion of lilte niaeqj|t 
•otan'ties, and Ihe attraction of unVike magnetic ^tAw'Hiw. 
Primarily, the relation between -magneUc ■ftcXawVa. i 



JOltB attract one anothi 
rfynamoa and molors. 

motor is dcpicfed schematically by Fig. 
B dUgram shown, 
Is the stationary 
t pole, (there 
■^s two, or more 
ml motors and 
0. with a coil of 
i magnet wire 
around it. This 
tcdves current 
Itallery B. and 

resultant NorUt 

die (ace toward 



1, wliMc A shows the 
curretit travalinfr around a 

coil of wite dt■ck-^^^'ie. or 

right-handed, wn!. ^■ 

neiic polt rcsMir 

Ai B, the curr. 

around the coil i- ■ 

or counter-elockivi^p, miii 

the magnetic pole rcsuitant. 

North. 

The fundamental law ia 
"Magnetism," is that '." 
poles repel each other, * 
On this law rests the op^ 
arrangement i 




P 

n 



has a coil of wire 

I practice), and this 
_ __... .3 current from the battery B, through the 

brushes of spring brass Bl and" B2. 
:Aii)tnntator or current reverser is represented by C, 
e, and consists of two semi-circles of brass or copperi 
rotate with the armature. Now at the instant shown 
M armature coil is creating a magnetic north pole, 
■mntiie potet attract each tether, the armature pole js 
toward the south field pole. At this insKint. however, 
bnutator has also moved, and the current through the 

a coil has been reversed, the negative brush bearing 
Opposite strip of the commutator, and the armature 
atel is south, instead of north, with the consequence 
E armature pole is repulsed or pushed away from the 
kt etc. 

readily ; 




bH motor for 
batteries, is 
Bg.3. This 
has ,a three 
pre- 



dead centre. The CidA V^ a r.-n.^V toCv 
pole) type. The field and attna\.vi.ie covN.^ a.^^ 




M Ml tfc e ana«i3r= ac J. a W 

ndds, etc. Tb« =»c«r Ak^ 
■l«l fcy Tig- i. 

' 6 slot 



SS. 



Bcfon KO'RS fsnbcr ^ wS &c 
crhaps adTisib)< to oefise ttx 

yojiino ant] a moKir. 
A Dynania. ifc« pRB«jile ol 
■ht<h ■»is JiscoTtredby 1 

Ikhkcl FjimtUr. in K^. b Ut 
Irclrkal mairhine for tti« coB««fsJm Of i«ec 
no electrical <DcrgT. 

A Motor, .tfce fnn^jAe ot «Uch ww icn 
^ed kt xn Exposition in Gerncuiv, tolf t 







^ff alternating or conslnntly levcrsitig cunent. i . __ 

Bnction to ihe direct current tnacliine, whose deliverod o 

Uways traveling in a constant direclion; one icrtw 

own as the positive, and the other as (he negative li 

Referring to the diagram Hg- 2, if tlie movio? a 

Ifolcs and windings arc driven past the excited field po^ 

change in magnetic induction between ibein wiH 

set up in the armature windings, a current of elri 

Whose strength or voltage, depends npou the ntiniifiL, 

Df wire in the moving roil, its 3M^|^evotiitions f 

interval of time: and thirdly ii|^^^^^BU|Ui oE tl 

^irld pole, in lines of force per squa^^^^^^pu^sectiot 

~" ,1 in anipTct i? rtepcndcnt ■ 



of the armature wire; about 600 circular mils per ampere 

ODimon allowance. 
;Heace, from the above, it is seen that, with a constant 
, strenglh, raising the speed of rotation of the armature 
he number of conductors in its coils, raises the voltage 
irered aod vice versa; in direct proportion to the mag- 

a of the above quantities, also the greater the area of th« 

in orcular mils, the gfealer the current pernnssible. 
In general, there are three principal types of motor or 
amo, as regards the arrangement of the armature and 
'. magnet windings. These types are known as the aeries, 

' Lnd compound, and are shown diagram ma tic ally in 










-^ 

1 


s 


H 


ocS 


)"J 



Fhe series machine has several gooi and bad features. 
I a motor, it tends to run awaj^ if the load is suddenly 
pOoved; but for fans, or other rigidly connected load, as 
Fltreet cars, etc., this motor has many ideal functions, the 
l*f one being its powerful starting torque, or power. In 
Perftl, its speed varies with the load, until with too great 
"' '■ will stop, and probably burn ciw\. 

..lunt machine has its fie\d minima toi\wttVt6. ->■«- 
fkHel with its armature, and \s t\ve moa\. vJi-ieX-J tw'i?.<yj«.'s. 



69 



ly, gradually increas- 
ing its value, as the 
motor speeds up. A 
diagram of a no-volt- 
age magnetic release 
starting box, is seen 
at Fig. 7, for a shunt mi 



Its popularity ta iliic to its nearly constant ipeed 
all loads, the ilrup in speed (roni no load [o full load, 
exceeding 3 to 5 per cciu. of ilic iiiiiial speed, 

Seriea motor* in small tiiet maj' be tt^j stuttd 
connecting direct to ihe supply circuit, but shuat 
with their low armature resistance thrown directly 
circuit, would swamp the line for current, until It ' 
sufficient speed to generale enough counter-ell 
force to check the rush of current at starting. 
A starting resist- __^ 

ance, known commer- 
cially as a starting r^^^,^ j\,- 
box, is connected in i,; ^ Cff ^^- 
the circuit, to permit <><■ ^j i-^ ' 
of feeding the current 
the 



In the diagrams, '. 

■ the main kn 
ich. A, the .at 
of the motor, 
erics or compc 
winding, and 
cgular shunt ' 

Compound we 
are tha 
having both series 
shunt windings, 
compound motor h 
most constant n 
type, while the c 
pound dynamo li 

generator, under « 
use, for the conn " 
imos. Wlien the 
nt travel: 




BTg, 0. 



ing loads. Ther 
of compound w 
field coils arc sc 



nid motors, or d 
:onnfcted that C1 
in tbe same direction as that in the shunt coils, thi 
are said lo be hooked-up "cuiiwlative." If the current pass 
around each of them in a different direction, then they 
said to "buck" each other, or they are hooked-up "^ffi 
lially." In operating as a motor, if the fields are * ' 
cumulative, then the combined coils lend to Strengthen 
field flux, as the load increases. The armature current pass 
through the series field coils, and the field flux in line* 
force is directly proportional to the number of turns » 
coils and the amperes of current traveling thr-ough lb 
Tlus is referred to as the resultant ampere-tiirnt, or 
times turns of wire. If the motor is connected up di&Cfl 
tially, then as the load current (armature current) increSB 
it would pass through the series field coils and bucking" 
resultant field strength would be weaker. This causcc, 
motor to speed up slightly, and so keep the mean speed f 
nearly constant. The draw-back to this method, howC 
Jies in ihe possibility of the load becoming so severe, t 
(Ae greatly weakened field wou\d cause \\ie malot to fa" 
Jts duty, and it would graduaWy come \o a _alop a.tv4^ 
out. The differentially wound machine w nti.\\tfc4 
10 



SVhera )ta peculiar characteristics are of great value. 
jfltA of any motor is increased bj 
^its field. This can be accomplished 
T of ways. The most common is to 
a resistance in the field circuiL A 
illlMable rheostat for this purpose on 
hines is the "Electro" Rheostat Reg- 
D at cut 9. This rheostat has a car- 
rity of two amperes, constant load, 
e is 10 ohms. The adjustment of 
:e is extremely fine, there being 
._ J steps in the instrument 
1 rheostat is also very useful for con- 
beting up in dynamo shunt field circuils to ad- 
ust the voltage. The voltage of a dynamo is 
pried by changing the resistance of the shunt 
1^ coils, by means of a rheostat; also the 
peed of rotation of the armature may he 




uds 



pres- 



Flg. 1 



o p iiy machine divid- 

d b 6 ^ives the equiva- 
h power output, and : 
divided by 1,000 
B h output in KUq- 

V, One YoXo-waxx = 

\.,4 ViOvaevowcT Qt ^^SM 
watts.) TT\\s ^!eneta.\Qt ^>a 




dticribcd will IJKhi up seven 18 volt TiaigalcN L _, 
time, llie machine 11 supplied in two vo1iag«s, . 
volw, 5 amperes, (80 waitsj or 6 *olis 14 amperes, I 
watts). 

ful little dy- 
namo known 
as the "Elec- 
ttodyti" is iJc- 
picted at fig. 
13. Its ouipiit 
at 3.500 R. 1'. 
M., is 7 volts 
on open cir- 
cuit. Safe 
maximum load 
4 vollfl, IJ-i 
amperes. 1 1 
will tight up 
five 4 volt 
Tungsten lamps, 
on 6 volts. 






For laboratory purposes, demonstrating, efS, 
power drive for small dynamos has been develojl^^ 
placed on the market. Its appearance is seen at fig.'l^^ 
as will be at once perceived, it is doubly compounded, 1 
to ,^rive the dynamo at greatest speed with the ""'■' 
exertion upon the part of the manipulator. Special spli 
belts are supplied with it, which prevent any ordinary tronli 




' dirtct curreni motors can sometimes be operated I 
ting currctii (single phase), by simply short-c 
( brashes by a piece of heavy copper wire, anJ 1 
Cm Ihcougli tilt? field winding. This arrangement J 
vtbat is commercially termed, a repulsion motor, J 



he (act ihRt th< 
'!^ rotor). 
Mtt til the 
l^es of ihi 






of the 

the repuls 
, by the c( 

leclcd as : 



1 of the induced J 
stamly reversinBrl 
tat^r. Small D. " 




s types of A. C. motors in use now, prin- 
iltCtion motors, repulsion motors, and the synchron- 
ic The squirrel cage induction motor has a rotating 
|Vilie no electrical connection with the main circuit. 
Ig member is much the same as an ordinary arnia- 

Kled of punched steel sheets, w^lAi -a. wmwCqw o^ 
^^ its periphery. In the slots ave p\ace4 xo\\i to-^- 
d-iU soldered or riveted to eactv ot.\\ec W ^^lt tnia 



of the steel ilruin. The constantly cbanginff Riajin^ 

acting Irom the slalor, or 
field portion, seis up or in- 
duces m arctic pa Ice and 
currents in the roior or 
armature. The reaction be- 
tween the induced rotor 
poles, and the eonatanilj' 
changing stator field drags 
Ihe rotor around witli it. 
Induction motors are sub- 
ject to a slight slip, or lag- 
ging behind the theoretical 

The repulsion motor has 
already been mentioned. U 
has its brushes short-cir- 
cuited, and A. C. is passed 
through the regular field 
windings. Usually there 
has to be a change made in 
the held windings for use 

on A. C. as the D, C. resistance is too great, owing U; 
self-impedance incurred when A. C. is applied. "^-^ 
A. C. fan motors are of this type. 

The synchronous A. C. motor is a constairt agcei 
running in step or synchronism with the supply A. C 
the motor. These motors are very useful for cei_ 
poses, where synchronous speed is essential- Tbeyi 
practically in perfect step with ihe supply currctn M 
are considerably overloaded, when they instantly'. 
of step or phase, and come to a sudden stop. Vn, 
tective apparatus should be placed in Ihe motor <i 
so that in event o£ their becoming stalled for any 




PIB, \n 



'wr.*v 



they will not \ 
ijuent heavy ci 
the main alten 
disastrous resu 



LESSON NO. 9. 
URGLAR ALARMS AND MISCELLANB.' 
OUS CONNECTIONS. 

rol of all electrical circuits is made possible 
c of some sort of mccbajiic^l current break- 
, known as a switch, circuit-breaker, etc, 
; to the style and function of the apparatus. 
witches are shown at figs. 1 and 2. These 
own as knife switches, the contact beinj; 



EMm^' 



FlgB. I mi] i 

d broken by a knife blade 
iw also of copper. T' 
ritcli is accomplished wnn- 
sboclb by means of the in- 
tan die shown. 
witch at fig. 1 is called a 
lie type, as it can only open 
■one^iole, or line of a cir- 
e BWitch at fig, 2, IB termerl 
i>pole type for the reason 
!an -control the two poles 

Erf a circuit. For some 
f the single-pole type will 
-1 Ifl Other instances the 

le form is necessary. 

r voltage work and small 

■' s."£leetro" Baby knife 




Ti 

The larger of the two^^H 
a double bladed knife.^^^H 
swing into a contact'^^^H 



n cuts 3 and 4, are 

very useful, 
switches has 
arranged to swing i 
at either side, giving quick controf 
of either one of two circuits. The 
smaller single-pole switch of this 
; and is equally serviceable. The dou- 
. s readily used to good advantage for the 
, light from two diSerent locations, as depicted 
Usraoi fig. 5. In operating this circuit, the switches 
", either to the left or right-hand contact, and 
either switch can 
then be made to 
; light or extin- 

^ I guish the lamp, 

r ] I n commercial 

wit <^sw.z lighting this is a 

standard arrange- 
way push-button 
or snap-switches, 
are env^\o'st4 vcv 
p\ace €s\ "i-Vt^t 
; \ow \oUifte "At- 



& 



A miniature snap switch for low voltage work is seen a 
5. This is very useful for low voltage lighting circuiUfS 
n rrijlica of the heavier built commercial snap awitcbeai 
current carrying capacity is S ami 
The cap cover is of metal, nickd § 
while the base is of porcelain. 

A variety of wood base and metat 
switches suitable for bell, and bS 
al:irm work arc illuslraled by i£e 
hi;s. 7 to 9, For making quick jl 
l)eiwetii two portions of a cin 
separable connector seen at fij 
Fig, fl serviceable. Thia connector is a-_, 

to any portable apparatus, wllich n 
iiccted to indepetident sources of power, when in use, ?« 

Having shown the different styles of standi 
a few words on the use of them may not be out qI _ 
The proper connection of a single pole knife switch 
a Itghting circuit is Indicated at 6g. 11 A. The COBSI 
for a double pole single throw knife switch is shown 
At C is one method of employing the multi-point 
switch for the control of battery power, supplied to \ 
cuil. Another use of the multi-point lever switch H 





field winding, t 
the doable pole, double tlirow knUe sVitA, lot i 
the field current, and al&o the lolalion ol V\vc 1 




tlic reversing switch connecled Up 
r wilh atmalure starting Tcsistance 
or is io be reversed, the compound, 
or series field 
winding is con- 
nected in scries 
with armature 



el e 



i\ 



{ hoxsB of the 



alarms, is that 
involved in the 
detection o f 
midnight prowl- 
ers, or burglars. 
The safes and 
.... L banks and private residence! as 

P'aa all windows and doors, are well provided with com- 
v'electrical alarm systems. In the following paragraphs 
7 of the best alarm systems will be discussed, 
pobably the very simplest burglar alarm circuit, is that 
TMing on the open circuit prmcjple, i.e., normally the 
^t is open, and the battery can be of dry or ordinary 
Jt cells. Such an open circuit system is seen diagrammati- 
"ig. 14. B is the dry or wet cell battery and S. is 
I ainele pole switch throwing in the battery, say at night 
fcre retiring, .\t W. W, W, W, are the window springs. 
Vclose Ihe beil circuit whenever a Basb is raised. D 
, ba'% door spring, which closes the alarm circuit whea- 

ritw'di 




Jh tte frame of 
jtkrm. At K 
^At cam shaped portion actuated by the sash as it raises 

( lowers. 

r alarm systems are usually arranged so that once 
JtiUtn bell has been started rinBing, it will continue to 
mntil shut off. irrespective of the position of the win- 
*Ct door spring. There are two ways of accomplishing 
f^fanctton: one is that employing a self-switching bell, 



rihe other by the interpositio 




relay drop, in 
The circuits of the 
continuous or self- 
switching bell, will be 
understood from fig. 16, 
which shows the ■work- 
ing details; S is a pivot- 
ed arm held normally in 
the open circuit position 
cans of the 
1 the arma- 



, by I 



projection ( 
ture of the bell. If 
regular circuit of the 
FIS.15 is now cVoaci, Vj \ _._ . 

ing the WV>.OTi t , "^t 
ivard the magnet cores, a-fti \n. %o iovn.'t 
oted arm S, wivitlA \s ^uaVti M.u>i-a-^Oi 

n 




againat the auxiliary contact tcrew V, Dnd the bell I __ 
complete workinfr circuit establislicd separately from 1_ 
push button circuit. It will continue to ring until shut g 
by a switch, or the trip 

Tiie manner of hook- 
ing it up in a burglar 
alarm circuit is seen at 
fig. ir, where S is a 
twitch: B the battery 
and W, W, window or 
Other alarm springs. 
The circuit is of the 
open type, i.e., nor- 
mally there is no cur- 
rent passing through 
the circuit. 

The closed circuit 
system of alarm is one of the best and most' widely «_ 
It has one great merit: that is. if a wire is cut, the beU-f 
start ringing, and as most of the would-be second a 
electrical experts cut the wires at the start, it is scec 
this system is indeed (juite meritorious. The maifi ] 
cnce in the closed circuit form of alarm, is thattbt 
is of the gravilyX 
closed circuit tynQ 
the Gordon ^i-Ca 
The spring e 
windows and doo^ 
nially closed 

I'he a'rmalure puUS 
Ihe magnets at ff 
When a window 3 
open-circuited 




broker 



vindoi 



the.>4 



leases its armaturi 

falls back against ■ 

tact screw shown, ck 
the bell circuit. The 
used here, may be a 
mon or continuous ringing pattern, already described. 

Some elaborate burglar alarm systems have a comb! 
tion of the closed and open circuit, enabling the alarm 
to ring, if the circuit is opened or closed at a door or 
dow, or if the wires are broken or crossed at any point. 

Electrical alarms are often applied to clocks, for signalling 
the starting and stopping time in factories, arousing put- 
poses, etc. A simple method of ringing a bell, or a nurobef 
of them, from a large clock is illustrated by fig. 19, 



many insulated brass 
as times it is required to ring 
the bell, in the fashion indi- 
cated. They are adjusted, so 
that the hour hand makes 
contact with them at the de- 
sired time. The bell circuit 
is closed through the hands 
of the clock and the contact 
screw. A simple and effec- 
tive method of making an 
electrical alarm clock out of 
an ordinary alarm clock, 
(which ordinarily refuses to 
alarm), is shown by the 
sketch, ng. 20. An insulated 
spring S, IS mounted on the 
filock movement, so that when thi 

IB 






around the disl. 




regii\at aXwm a<>t* J 




pit- B'ailually Cxpuitis and nukes contact ' 
l spcin?. Thi» closes the bell circuit and 
to tiiig until shut off by the switch which may ] 
e bed. The method of making cfintact in ih* 
po«itIvi?, and in no way hurts the clock move; 
KHftnt* capable of giving an electrical alairt 
Iperature in a certain location has reacheil i 
arc cJasscd under the head of "thermoslatt." 
ma of thermo- 
made of a eom- 
ilrip of two dis- 
tal, such as iron 
jper, arranged in 
laer shown by fig. 
' sketch S. is 
Oinpound strip, 
"'l iBcil wide ani 
I long, witli the 
[^similar metal 
8-. riveted togeth- 
("fcc temperature 
strip having 
atest coefficient of expansion per unit length, tends 
rfi the compound strip toward one of the contact 
JC It or C 2. By means of these adjustable screws, 
nbostat may be set for any rise or fall in tempera- 
id when a certain degree has been reached in either 
t, the corresponding bell, A or C, will be made to 
I'lB'thi! battery common to both bells. In the place 
6^9 may be inserted a relay, for the control of 
■ett. A common use of thermostats with bell alarm 
(Chouses, where it is desirable to keep the tempera- 
nreca certain limits at all times. 

&r form of thermostat is the mercurial type, built on 

e ^der as the everyday thermometer. Fig, 22 shows 

[e«p of this pattern, consisting oE a glass tube and 

led with mercury. As the mercury rises it eventu- 

iches the sealed-in platinum wire A, and closes the 

[t through battery B; the either pole of the cir- 

d into the mercury through the scaled in plati- 

C. This 



I very good fire 
llenOOstat, hav- 
top platinum 

n with the tcm- 
e mark, of about 

115 degrees. 



work, a. special 
it Aermoslat is 
There are sev- 
le now In favor, 



c 



H<|t— ^® 



thin air light metal chamber. When the 
ralure increases to a certain point, the ex- 
in the metal chamber causes ks -MiW to 
doing', it closes an clecU'icaA l;ltc^i\^.. T\it 
MKarewcll distributed throughout v^ie buiiA\TV% "«\i\d& 






w^r^ 



ihey »re designed t 




protect; spacing lliein from 10 10 U 
apart on the eeSioi 
diagram of a coa 
cial Bre alsrn tnft 
tion is depicted «t 
23. The varioos $rt 
of thermostats i" 
ferent sections 
building, i 



vith 

which indicates 
what section an aj 
comes from. The 
cuit also inclndci i 
lay and clocla 
sending machine. 
Now if a fire occurs in any of these sections, tb*' 
causes the air tight chamber to close the circuit, tfcfl 
the battery B2, switch SW, (here shown open), alajiq 
dropi magnet D, clockwork relay R. and the annunciator 
magnet corresponding to the section from which the I 

In practice fire alarm 
systems arc tested reg- 
ularly, at 30 day inter- 
vals, to Bee that they 
are in perfect working 
order. The clockwork 



CI, 



leased by a relay mag- 
net, controlled by the 
line relay R. Its spring 
motor drives the toothed disc F, 
rotating, it passes by the fixed 




CLOCK MOVeMCir 
SPRINe 

ns.ao 




COMPOWND STRIP 



brush P, 
pre-arranged set of 
nals or rings, 
transmitted t 
hcadqt:arters. 

Another class _ 
tomatic alarm or li 
is that employed 
indicating the higit 
low water slaffCS 
water tank. Thei 



Ft6.21 



Whei 



, the ball H, (and water), 
permissible, the arm L, pivoted 
and rings the high water bell 
B. When it sinks to the low 
water limit, it makes contact at 
D, and rings the bell E. By 
substituting relays for the bells, 
it may be arranged so that the 
water and ball float open and 
close the water feed valve. 

The connections of the vari- 
ous wires in electrical circuits is 
of great importance. The joints 
should always be soldered to en- 
sure permanent working connec- 
tions. Unsoldered joints, espe- 
cially oa low voltage circuits, 
such as bell systems, present a 
high resistance to the passage o\ 
A curj-enf, and sometimes become 
I «0 



~^ mon scheme lo 
^ ranging this alai 

by means of s. 

float, as in fig-. 

e to the highest 

P, makes contact 




I passes at all All j< 
^tiically and 
lectrically perfect, 
pfore soldering. 



idea 



of 




1 



fcl'""' ■ 


M 


A ^ 




|6"| SW 





i of a blow torch, the "Electro" 
setf- 



of forra- 
glS Joints on wires 
be gleaned 
I an examina- 
Jbn of iig. 25, 
l^or soldering the 
^nts a regular 
^dering copper 
be used, a 
_e outfit in- 
bding copper, 

felder and Rax 
ping illustrated in 
I 27, this being 
s "Electro" set. 
^For soldering by 

blowing torch 
seen in fig. 26. 
will he found 
very useful. It 
burns 2 hours 
with one filling, 
and uses alco- 
hol fuel. 

For joints on 

copper wire, any 

standard flux 

may be used to 

make the solder 

take hold, such 

as the Allen or 

No-Korode 

compound used 

by the electrical 

trade very ex- 

bsively. Before attempting to make & soldered joint, the 

(faces of the metallic wire must he thoroughly scraped 

no, either with, a knife or a piece of emery cloth. Having 

ted the juncture by the application of a hot soIderinK 

' torch flame, the flux may be applied, and 

the solder. 




_ s! d c 
. U 1 d run 
lough the joint 
woughly, and 
^nneate all the 
involutions of 
girc When 
^d, it is usually 
>ed with black 






„ lighting 

nrfc all joints 
(jjfirat' covered 
1 gum rubber 
!, and then 
pth black fric- 
>B vfpe. Paint- 
s' (be (ape with 
* aspiialtum 
•Mic tends tc 




A.c»is Q^ a.'n.-s Vvtvi 



W LU ' 



never be used for iiny dei-trical joints as tliey sool 

llic metal. Auj iroulOc experienced in tinning ihc 




3 



al conductors are furnished with a I 
This makes the wires much easici 
1 have to be tinned with the soldering i: 




lesson no. 10. 
"Experimental electro-physics. 

|HE physics of electricity would not be complete, •nmtl- 



and s 
the n 



I summary of the early history . . __^ 

; i>p«ninK paragraphs have been devoted to 
interesting ^ochs in this connection. 
r ago, before scientists had begun to eveik 
faintly understand the phe- 
nomena or meaning of elec- 
trical manifestations as they 
Occur in nature, it had been 
observed that when amber 
was rubbed with certain 
other substances, so that 
friction was created, the 
amber exhibited 'a new prop- 
erty, viz; that of attracting 
and holding small bits of 
thread, hair, straw, etc. At 
that time, it was thought to 
be some mysterious force, 
efe 



signifying 



"harpaga, 

harpies, or "a thing that 
Iches." The origin of this odd cognomen, was due to 
. dbcovery by the women of Syria, that the amber distaffs 
Spindles, forming part of their spinning wheels, tended 
Bitract small parti- 
I of thread, straw, 
, when the spinning 
. " had brushed 
nsl the amber for 
Ktrt while. 
_ e word amber, and 
derivation has not 
-slablished 



l^, but it has been 
')ed to either i 






/«» H 



r 

>• ^^ 



.1 magnetic ore, as found in the 
earth, were not unknown to the 
ancients either, having been 
mentioned in the writings of 
Aristotle, who ascribed to 
Thales of Miletus, chief of the 
f^ Seven Wise Men of Greeee, and 
who was the contemporary of 
Aesop, the view that the action 
of amber and the lodeatone sug- 
gests the existence of an "alter 
ego," or soul, in these sub- 
stances, meaning undoubtedly 
when philosophically interpret- 
istrued, an inherent force independent of any ex- 



F16.3 



il agency, 
ccording to the legends and traditio 
I were at one time the wisest peopli 
lerties of the lodestone or 
X?l magnet, were known H 
• two thousand years before 
dawn of the Christian era, 

iboldt relates, in his "Cos- 

¥that the Chinese employ- 
e Jodestone magnet 



of the Chinese, 
n the earth, the 



(z: 



a small 



16.4 @ 

voyages, the magnet, \va.VHv^'\n;MvjjJ^^ 
g device, -wViwAi """ 



point continually in the same direction. At) the iw 
wnlings on the subject, however, were of little prac 
Ufnificance, and it was not until the I4th centtiry, that 

scientific application of electrical phenomena took any 
nitc ihape. 

As nearly 9s known, it was about 1320, that Flavis G 
a native of Naples, Italy, invented the compass that we I 
ally have record of. This instrument varied from the 
north, but Christopher Columbus and Sebastian Cabot ai 
to this knowledge, that which can certainly lie cJ&imci 
important scientific facts. From time lo time, otb 




tered facts and phenomena were observed i 

but to Dr. William Gilbert, born in 1543 at ColchelJ| 
about SO miles northeast of London, England, 
credit of first publishing a book, giving a connected accOJ 
of electromagnetic 

Among the foremost of Dr. Gilbert's discoveries, was |j 
our globe, the earth, was in itself a great spherical r 
For this important discovery, Gilbert received great prj 
from the eminent astronomers, Galileo and Kepler 
many others. 
Static electricity is the usual (orr 
and is rf/stinguished from voltaic ot galvanic t\ec\.i\sj 
its exceedingly high voltage or polentia\, an4 S15 " ' 
value. In fjs nature, static electrVcity ' 



IE 



iter form. Eleclricity in other form usually ile» 
enis continuously, but static 
I'ectricity is accumulated in 
^ndeosers and its discharge is ^ ^„ ^^_ 
istantaneous, as ivhen light- 
ing passes from one thunder- ,,^, , 
bud to another. The static 
snerator and experiments with 
are treated exhaustively in another chapter. 
The first scientist to build a frictional machine for the 
cneration of electricity, was Otto von Guericke, a Gcr- 
About the year 1750, he constructed a rather crude 
lachine, comprising: a rotating ball of sulphur^ which when 
leld between the hands, produced electricity by the fric- 
on incurred. 

Prom this experiment, the static generator was slowly 
iproved, until it finally reached the form of a glass plate 
■otating between leather cushions. The friction ihui lel 
ip created electricity, and later a condenser was connected 
o the machine to collect the electricity. A cut of a modern 
latic electric generator is shown in Fig. 1. 
Other sources of electricity besides the static machine, are 

I follows!— 

Percussion, — If 2 violent blow is struck by one substance 
rical slates are produced on the 
two surfaces. Vibration can 
produce electricity, as demon- 
strated by Bolptcelli, who 
showed that vibrations set up 
within a roi! of metal, coated 
with sulphur or other insulating 
substance, produced a separa- 
tion of electricities at the sur- 
face, separating the metal from 
the non-conductor. Disruption 
and Cleavage; — Tearing a card 
apart in the dark produces vis- 
.__ sparks, and the separated portions when tested with an 
,ectroscope, will he found to be electrically charged. Lumps 
' sugar crunched between the iceth in the dark exhibit pale 
ishes of light. The sudden cleavage of a sheet of mica also 
t>duces sparks, and both laminae are found to be electri- 
id. Crystallization and Solidilication: — A number of dif- 
rent substances, after passing from the liquid to the solid 
ate, exhibit electrical conditions. For instance, sulphur 
scd in a glass bowl, and theri allowed to cool, becomes 
rongly electrified, as made evident by lifting out the crys- 
iiline mass, with a glass rod. Another substance becoming 
lectrified during solidification is common chocolate. When 
lenic acid crystallizes out from its solution, in hydro- 
loric acid, the formation of each crystal is accompauied 
V a flash of light, du; most likely to an electrical dii- 
faarge. *Combustion; — The 
cneration of electricity by 
>mbuslion was demonstrated 
' Volta. A piece of burning 
latcoal placed in connection 
ith the knoib of a gold-leaf 
laetroscope, will cause the 
laves to diverge. Evaporation: 
-When liquids are evaporated, 
leetrification often occurs, the 
quid and the vapor assuming 

''t states. Atmospheric Electricity: — This is closely 
'ith electricity of evaporation, and is the atmasQhecK 
large always present in the air, and due, m 'oW. W, \«l'«., 
evaporation going on over l\\c occa-ns, ktivms^ "Ekw: 








na. A 



» tiowe't CempeadlUDi oC Apvlled KleclcVcAILs- 




inhabitinff 
^ '^— -- 

. „ I 

ot thwe are the "Torpedo," the "Gymnoli 
"Silurisj'' frequeniing the Nile and the Niger Rivers. 1 
"Kau Torpedo," or electric ray, of which there are till 
fpecies inhabiting the Mediterranean and Atlantic, Is p 
vided with an electric organ on the back of its head. * 
organ consisti of laminae composed of polygonal eelU 
the number of 800 to 1000 or more; and supplied with It 
targe bundles of nerve-iibres. The under surface of the i 
ii negatively electrified and the upper side poKitivel)|. 
the "Gymnolus Eleciricus," or Surinam ee!, Phe electric . 
gan extendi the whole length of the body, along both >Ml 
Be leen in cut 2. It is able to give a most severe shock, a 
provec itself a very formidable antagonist .when it hx i 
t&ined its full length of 5 or G feet. 

It has been shown that t 
nerve excitations and muscttl 

aUo produce feeble digch&ff 
of electricity- There it also t 
electricity of vegetabl 
thermo-electricity, contact 
dissimilar metals, and otl 

Magnetism, the basis of mi 
all commercial electrical aj)] 
ratus to-day, is a very intere 
ing subject. As aforemi. 
lioned, the properties of natai 
magnets or iodestones w 
found in Magnesia, Asia Mim 
and was called the ma 
Stcne, owing to the name of the country in which it 
found. The properties of the lodestone may be convey 
to other substances such as iron or steel, by friction 
rubbing. Nickel and cobalt are also slightly influenced 
magnetism. 

Steel was found to have the greatest retcntivity ot hol 
ing power for magnetism, and hence it was always emp16]r 
for magnets and needles in mariners' compasses, in the ei 
days as well as now. Magnetism, like electricity, reqiiii 
mailer as its medium through which to manifest itself, t 
the present theory is that it is a mode of molecular ttuSti 
generated by vibration of the molecules, and unduIation( 
the alt pervading luminiferous ether, which permcfLt^..' 
natter and fills all spaces not already filled by otfier .|i 



riG.9 




Pig, 10. 



stances or matter. The s 

of electricity through the i 

or in the metric scale, it is equivalent to 300,000' fcilomct 

*r XIO.000.000 meters. 

, There are two common forma oS peviua-ivcnT. sxtt\ laa.^^ 
ia ase, one 'being; the horseshoe s^lape and &t ofeti 
ftnight bar. The former is seen at ¥ig. 5, ai\4 r.\ie \ia,t ■ 
86 



^^Jl. 



Magnets, no mailer what their shape, are 
way! jurrounded by a "field of force," as it is termed. | 
insed by the magnetic flux or lines of force tending I 
*urn from the north pole to the south pole. To reaii: 
efficiency and life, the magnet should hai 










P0u\fi/7r i^ fLECTfio *Mare:xj' 



)inpiete path through 
I is supplied with horseshoe 
ia^neta, and when not in 
:e (he keeper supplies a 
W resistance path for the 
IX, thus preserving the 
agnet's power. 
The appearance of the 
lid of force about a mag- 
jt is seen at Fig. S. Sudi 
flux diagram is easily made 
~ any magnet by sprinkling 

e iron filings on a piece „, „ 

glass, and placing the *" 

ignet under the g'ass. Tapping the glass gently will serve 
make the filings evenly distribute themselves, when they 

ly be photographed, or a print may be made direct by plac- 

; the printing paper under the glass, and exposing it to the 

Every magnet has two poles, each of opposite polarity 
lure. They are designated respectively, as the north 
outh poles. Like poles repel each other, and unlike 
Dies, attract each other. The end of the compass needle 
Kgnet seeking the earth's north magnetic pole, is really 
louth pole of the needle magnet, but is often referred 
: the north pole of the needle. North-seeking poie is 
ore correct. The principle of every magnet having two 
Mimilar poles is made more manifest, by breaking a bar 
Other permanent magnet, with the result shown at Fig- 
As seen every individual magnet has assumed two un- 
ce poles at the ends. The best way in which to observe 
le changing action of the magnet poles, is by means of a 
■nail compass or magnetized needle, pivoted, so as to swing 
eely about a fixed point. The north -pole of the magnet 
usually marked in some way, either by an arrow head. 
IT by bluing it. If such a needle is presented to the poles 
rf the horseshoe magnet seen in Fig. 3, the north and south 
loles of the needle will be attracted alternately. The poles 
(f an electromagnet can thus be tested also. 

There are two methods of making permanent magnets 
rom hardened steel bars, by direct touch with another 
lermanent magnet. The first is known as the single touch 
lethod, and consists in stroking the steel bar A, from the 
litre to the end, in the direction of 'he arrow, removing 
; magnet B, returning it through the air to the centre, 
.d {with the same pole) again stroking it to the end. The 
olarity induced in the bar A, is of course opposite to that 
Kisting in the magnet pole B. as indicated by the polarity 
gns in the sketch. Usually 15 to 20 strokes are sufficient, 
hen the olher half of the steel bar is stroked with the oppo- 
ite end of the magnet B, from the centre to theend, as 
reviously, and a similar number of times. Magnetizing by 
mblc touch is accomplished by using two magnets, as in 
g. 8, and both poles {of opposite sign) are moved from 
B centre outward, simultaneously. About 15 to 20 strokes 
re sufficient. The steel used for making permanent magnets 
lotjd be very hard, such as Tungsten steel. The harder 
;e steel, the greater the retentivity, also the strength. 
Steel magnets are best magnetized, by placing in con- 
,et with the poles of a powerful electromagnet. This 
the method pursued in most commettia.1 ii.s,t% lA 'Ocatp,, 
IpMjaJJy /or magnetos. Sometimes \\ic^ a.xc w^-i^.^s.'Oa.tft, 
'winding a coil of insulated copp« Vvtc ^XDM.Tvi <r- 
i then passing current through Vhe cov\a. ■Vi-aXva.'f^ia. 




net 1»rB may be magneiiicd by direct toacb with anal 
U-ihapcd magnet as shown in Fig. 9. sirolciOK tlie new n 
" from the poles to the U-bend, of vice versa. 

All eleclrieil conductors whe 

carryiiiK current, are surrttundei 

by a magnetic field of forte, i 

depicted in Fig. 10. Here tlf 

current (direct current) i_ 

shown passing away from (hi 

observer, that is. the end ntii 

est him is positive, and then tL 

whirl of magnetic force or flo: 

is right-handed or clock-wiu 

facing the near end of tire c 

ducior. If the current w _. 

coming toward the obierref 

the whirl of magnetic f 

be leFt-thanded, or opposite t 

tha't shown. 

The effect ot winding Ihe conductor into coils about aul 

net poles of soft iron, gives the result seen at Fig. 11. Till 

shows that if the current passes around the coil clock-wU 

the resultant magnetic pole is south; but if it passes a ' 

the coil counter-clock-wise; then the resultant magneti 

pole is north. This is one of the most frequently occurriT 

niles in electrical work of all kinds, and should be w 

memorized. 

Probably -one of the most interesting and important lat 
in eleciro-physics, is that there is a direct relation bctww 
magnetism and electricity. Magnetism and electricity it 
reciprocal or interchangeable and can produce each otbei 
which may be readily shown by suddenly plunging a ,_ 
manent steel bar magnet into the interior of a solenoid 
or coil of wire, as in Fig. 12. Connected to the coil of wif 
is a galvanometer CM, which is easily made by winding,': 
eoil of a dozen turns of fine wire about a small compass CH 
as seen from the detail, or the "Electro" Galvanomete 
can be employed. The coil of wire is placed parallel' to ft 
needle of the compass. This makes quite a sensitive fiSB 
van a meter. 




Fie. 12A. 

Now if the steel magnet bar M, is suddenly plunged iot 

I the coil of wire D, a deflection of the galvanometer needl 

F will be noted. Upon withdrawing the magnet bar from ih 

t coil D, another deflection of the galvanometer needle ^1 

r be noted, but in the opposite direction, lo that of the iin 

ction, occurring from the insertion of the magnet. Thi 

e principle upon which transformers and induction co" 

operate, the second cotl of wire being placed outside ti 

coi! D, shown here. Instead of moving a permanent st< 

magaet, in and out of the coi\; the roagntimng ointfiV 

L tbe coil D, is made to pulsate or a\lernave gwmg xVc sa 

Ksalta. The core is stationary and o( tVie solusft won 

8« 



r-r 



E all the magnciisni possible, at each change 
[Instead of using a steel magnet, a soft iro 
pth a magnetizing coil, may be used as al Fig. 12 A. 
B0W9 the generation of electricity from magnetism. 
pnstrate the production of magnelism from elec- 
\ is only necessary to pass current from a battery 
Ipource ihrotigh the coil D, when the magnetic force 
'tithin the coil, will suck in an iron bar. A perma- 
i core fastened within the coil, makes it an elec- 
;t and this is the basis of the aclion of the great 
ra, and motors turning the wheels of commerce 
KVhen an eleOtric bell sounds, an electromagnet has 
[the hammer. When a spark several inches long 
I gap connected across a transformer, electro-mag- 
beeu responsible for it. 

lel Faraday, we are indebted for a greater part 

Eowledge concerning magnetism and electricity and 

: inter-relation ship. Faraday was the first to show 

tftism could be changed into, or made to give 

ent, when a magnet was acted upon by raechan- 

He discovered that a coil of wire when moved 

I a permanent steel magnet or active conductor 

led in it anolher current, and of opposite di 

If the inducing current. This great discovery by 

[was taken up by others, and the real development 

bal apparatus employing these principles, had been' 

%*»« way. 



11 

in core^^"^ 
■. 12 A. ^ 



LESSON NO. 11. 

ECTRO-THERAPEUTICS. 

City has now become a permanent adjunctj 

medical practitioner and surgeon, in ■' ' ' 

l^tive duties. Every hospital of any consequence 

[■day, has a complete equipment for the application 

w, High Frequency currents. Cautery currents, etc, 

le methods of applying electrical current for certain 

applicable by the patients themselves, 




-B- 

''i"i!!i'M 



1 general this i 
[Chances for the 
\ except with thi 
escribed further 
Ifclnds of 



not recommended, as there are 
unexperienced to do more harm. 
Medical Coils delivering Faradic 



are employed for electro-thera-, 
•k, the principal ones being as follows: 
Current, which is ordinary direct current derived 
from a direct current lighting circuit, 
Oirrent, which is usually imderstood to wve's.tv. \.V 
lltemaling, pulsating, cuttcnt 4e.Vwfttti. \.\> 
" Ldinu of an induction ov KvtiVcA tci., *■* 
lown. 




iiiftueiiL-e machine 
the Holu, or Win 
Oudin and D'A 
Currents, suppliei 
higli frequaicy " 



isfoi 



i. oil 




type; the potent 
frequency betcij: vi 
Tlie use and j« 
of Galvanic or low 
direct curreats 
considered first *! 
strength employed is measured 
_ mperes, one milli-ampere being equivalent to _ 
thousandlh of an arnpere. Hence a current stretiKtJ 
milli-aniperes is the same as lOO-lOOOtlig or 1-lOlh. 
The resistance of the human body, which is confin 
cipally lo the skin, ranges in value between 2,000 
ohms and higher, but 
this is dependent to a 
ereat part upon the 
condition of the skin, 
nature of the elec- 
trodes, and area of skin 
covered by them. For 
all galvanic applica- 
tions it is necessary lo 
keep the body resist- 
ance down as low as 
possible, and' this is 
greatly facilitated by 
first washing Ihe skin 
with soap and warm 
water, afler which the fft-3 

skin surface is wetted 

with salt solution. The electrodes used should haVe 
a contact surface as possible also. 

Galvanism in most cases is applied locally, the 
applied to the diseased portion being known as the 
Electrode." It is generally of small size, as compaxf 
■ Electrode, " which is the cognomen ajmlicf 
- "-"— ^1 terminal. 

of sheet lead « 

I, afterwaxit v 

with Sevferal 

surgical 

ked in salt i 

is electrode 

y applied 

stomach oi:.abd< 

the patient. 

way to form __ 

sive" electrode, 

have the path 

mcrse the feet _ 

of salt solutia 

solution being rl 

electrically activ 

small metal pla 

"■-■' -nto it, b 

ig the pa 

1 ne arrangen 

the galvanic cir 

■quired) is depicte4 

heostat or slowly adjust 



"Passiv 




oil; B T the liallery of wei or dry cells; M A,, 
permeter or simply tnil-amineier; A E, the acty 

Id be applieij lo the diseased portion; and P E, 

electrode 
s a. tub 3t A 
{ram B a 
lint selector 

shown for 




Sl Galvanic and Faradic Switchboard as supplied 
lerciiLl purposes is depicted by fig. 4. This switch- 
board is for use with 
BULB ELECTRODE batteries and has in- 

duction coil, rheostat, 
necessary switches, in- 
terrupters, etc., com- 
plete. Other styles and 
forms of control board 
are made for 110 volt 
direct current circuits. 
All work of this nature 
should be done 
methodically and ac- 
curately, to avoid harm 
to the patient: and for 



POINT ELECTRODE 



aients, the mil-ammeter i 
bving shown by fig. 5. 
f the commonest treat 
►tlon." This has ; 



^ntia 



t of a 



tand- 



tectrodes .. 

md covered 

gical gauze, 
with salt 
i o n. The 
(Negati 

applied 



FI^. 7. Needle Holdec for Neeslive Elecctolysla 






|HBi>i<"<.M ^J.^. ...^ upper part of the spine, and the 
Positive pole), over the abdomen or stomach. The 
ntrenglh apphed varies from 20 to SO milli-amperes, 
g ovfir a period of about 25 minutes. In applying 
currents, the following procedure should be adhered 
tiectrodes are first placed in contact with the patient's 
tn the current is turned on and gradually increased 
!Sired value. In slopping the treatment, the reverse 
that is; the current is slowly reduceA \o xtio, v.^!i 
t, removed. 

of "Local ga\vanizatiov\," \s eTOV>.o^e^& jg 
, Rheumatism, acute and cHrowic —"i^ 




the aBecl_ 
the passive di 
being Ihfl ' 

active eieciPL 
determined largely by ihe disease tif be treated. Tfc 
effect of the positive pole, being sedative, hcmostatie^ 
cidal and tending to relieve congestion. The local d 
the negative electrode, on the contrary, is productive i 
gestion, local stimulation, and counter-irritation. 

The treatment called "Negative Elecirolysis," bad 
live process, causing diseased tissues to soften and 
grate, due to the chemical action of caustic sodK 
gathers about the cathode electrode as a. result of the 
chloride in the tissues of the body. If a galvanic CMI 
passed through the body, the sodium hydroxide Or 
soda, collecting at the cathode electrode, will desti 
tissues in immediate toucli with the latter, and wltti 
them into a soft soap-like substance. 

"Negative electrolysis" ts applied for many 

plaints and ailments, such as iho eliminalion of giln 



in lis. 



the shape 



electrode to be used 
in removing super- 
flous hair. Its 
smaller end is bulb- 
shaped, tile material 
used for making; the 

steel. An insulated 
holder for manipu- 
lating the needle is 
seen at fig. 7. 

First the bulb- 
shaped electrode or 
needle is carefully 

entered into the "follicle" , 

magnifying glass if necessarj^ to locate the needle's p 
At this juncture the current is gradually applied by a 
ing the patient to slowly immerse his fingers iiitO'it'.l 
salt solution, containing the anode or positive electros 
current appHed varies from 1 to 3 inilli-amperea, Baif 
white bubble, no bigger than a pin head shows at til 
of the hair follicle, the patient is told to si o wl:? ,■!.-.-_ 
his fingers from the solution. The next part of ttie'opi 
is to remove the needle, and if the action has been C" 
the hair has been disintegrated from its root, and I- 
light forceps can be used to slide the hair from this 





..lethod of applying tVie tune'QV ani s^o^tito^ 

foll owed as given above lor remoVmg s\\pc\ftviDuaVsp 
" electrode, ccmnected to ^\ie ■ne^i^'i 



frcuit, te Insertisd in the growlli ""^^^^Ints legs 
atCied unlil il nearly passes tliiunsli Jl-^^ii^ 
kpplTcd by allowing ilii* patient to atowly imtnc! 
iU6 B-bowl of salt solution as prc\no«sly insirueTe? 
'rent is increase! to as high as IS niilli-ainpcres if 
y, to cause tlie whole growth lo becomt of a wliiie 
I color. Ill cases uf large growtlis, large; thati % i 
r, the needle can he applied more than c 
licaKon, being t!iat with the needle iiisc 
(lie fiist position. Antiseptics sliould not be apphd 
Towth generally dries up into a brown scab, and fa)| 
i own accord iu a meek or 

inoving targe grovrtki, such as birthmarks, and \ 
ipeciial multipliL pointed needla is employed; ^jaC 
3n« depicted at Fig. 10. The needles ar/insw,. 
ly at different angles, until die whole area has £n^ 
ikchcd and destroyed. 
tradic current, supplied by medical coils, which a 
[C Biwcially wound ifidufllion coils* or transfonntl 
lively employed both by physicians, and patients 2 
depetidciilly. Several slyles 3 

.j^ B ted by Figs. ■ . ... 

ff|P H coil shown at Fig. 11 docs r 

5^ ^ Wk deliver a faradic or sccondtdj 

■ent, hut an interrupted g 

ic or pulsating current. T 

scfn! to treating; rht'umalisvt. 1 

The coils shown at Figs, 
ind 13, both have secondary 
dings and deliver a regular 
faradic current, which as slated 
before is . an un symmetrical, 
' alternating, one of low fre- 
quency; and voltages of 1,000 or 
less lip to 5,000. according to the 
number of turns on the second- 
The current 
peres of faradic current applied, varies 
iotisandth up to one mili-ampere, depending 
iiie and length of the secondary coil. 
faradic coils, operate well on 2 to 4 dry cells, but 
As they are operated directly from direct current 
tircutts. 




■Jjslological effect of faradii 
lage and frequency of iiiterrupti 



r neri'cs chiefly, 
USCUlar con- 
. ..'.!'._ . current 
ifi voltage, but of 
inency, causes 



rent^™ 

m 






\ia- termed "lela- 
Ttonic spasm." 
jioifntial faradic 
for 



lent 




>— imiiii 



FtG.-]-4 



*e of high 

Currents of this 
t are particularly 
ft treating cases 
ptgiO, Sciatica, also . , .. 

I of oculc pain, except those connctVcA ■w\'Cci n 





-'Septic Infection. Low TensLoD, I*w4 
(] u e n c y f TH^ 
currents, an fl 

lo increise ti 
cultir grotetk, 

duf to rluumt 
etc., Knd all 
producing B 
tar coDtracigj 

crrise. in cuei| 

partial han 
ac. The 
potetiiial fan 
current, K . 
ployed wilb fi 
intcrruptg 
speed, may p 
(lisastrou*, i 
exhaast ra til 




Fig. 1 



. A Powerlul Si! 
tnedium potential faradic current can be appli 



han iiivi0 



isclcs. 
either ^ 

or fast interruption speed, for the purpose of increasHig c 
liotl, and relieving congestive headaches. 

The polarity (apparent), of the faradic current, d«ii 
by induction coil secondary windings may be teslfi 
means of polarity test paper. The circuits of a Earadl^a 
including secondary and primary windings are shown i 
gram Fig. 14. These coils usually have three binding p 
2 and 3, connected up as shown; to enable the 
up the electrodes, for either galvanic (interrupted prfc 
current, posts 1 and 2; Faradic (Secondary) currenl^pqj 
and 3; or a combination of the two (Galvano-'- IjCj i 
rent, which lias been used successfully for treat . of j 
sfipation, enlarged prostate, etc. 

Static generators are extensively employed tor treat 
of various ailments. The current from a static 



r^ rectional, of fan 
■^ potential, but ' 
small amperu 
The curi 
therapeutic {■ 
poses averages \ 
Iwcen 10,000 
100,000 volts.. ■■ 
current deoslQ 
^O from one 

sandth to two'^ 
i! HiEh Frequency amperes. T&el 



r- 



g>T-'Hri 



^m 



thei 



olv 



, the hi{^ 



tile amperage; the greater the plate diam 
voltage. 

Static insulation and static breeze are two forms of t 
meni by this current in wide use. Static insulatio 
hath, is accomplished as shown \jv '^^g- ^&> ftwt "? t 
seats a platform upon which ihe pauem's boiv ^ te^l-V j 




This is of ose in treating Headache, /ocOl 
Ntrvinu ^fig'!*, and in Neurosis. The p *^ 
', giving a negative btetze, but the fors 
L as it creates less irritatioo. 
jfoppljing electricity in electro-ther^euiics L 
Qw. is by means ct high frequency apparatd 
I of Nikola TeaU, D'Arsonval, Oudin, 3 

I frequency set is diagramed at Fig. 
.former raises ilie primary potential (. 
It from 100 volls, at 60 cycle frequenq 
t 60 cycles. A is the alternato 
Qwer, In the closed oscillatin_ 
Vlaie or 1-eyden jar condenser C. sparjc^ 
r coil P, of the Tesia air core transformer, 
J of ihc current is raised owing to the 
1 discharging of the condenser across the 
; the frequency may easily reach 100,000 
ore per second. The potential is sensibly the 
next transformation is done by means of the 
, which increases the voltage to 200.000 or 
ftequency remaining Ihe same, i. e., 100,000 cycles. 



•j ; :: ^ =ie,C 







© 



which u 
mcntary i 
It is du« 
'seU "Z 

of Ihe coil, and is the resuU of the following acti 
fcrring to Fig. 1. the circuit of a wipe spark coil, wit] 
B, and make and break contact C, is plainly sho^ 
the contact is closed, Ihe battery current flows'aix 
coil, having the soft iron wire core within it, and' 
magnetizes the core. At the instant the contact bt 
circuit, the magnetism in the iron core collapses or A 
very quickly, and this rapid change in Ihe value of 1 
netic flux, causes a current of great instantaneous Va 
generated in the coil or winding, and this is the ciirPt 
"ing the bright spark seen on quickly opening such ■ 
It has great calorific or igniting value, and is mudi e 
for lighting gas jets, exploding gas engine mixtUKB, 
two metal handles or electrodes 
arc attached to either side of the 
break contact, as indicated by the 
doited lines, in Fig. 1, a shock will 
be felt, whenever the circuit is 
broken. The self-induced break 
current, is often termed a "kick 
current," in electrical parlance and 
the coil is referred to as a "kick 
coil" or "inductance coil." 

In Fig. 2, is illustrated the com- 
ponent parts going to make up a 
coil of the "induction or jump 
spark" class, having both primary 
and secondary windings, together with a spring vib 
interrupter, for making and breaking liic priman 
The connection of the various sections with the 





e eparkiiig _ _ 

iJeinagnctizing the 
n the gee- 
winding: 
luicker the 

the more 
ic«<I the 

coil. The 



)r»kB the 
and hence 




the 
screw, 
.„ the circnit again, much the 
-Itric bell. This keeps up as 
ed to the primary coil. 

\yacBl action of the induction coil is primarily due ti 
tbai a Current passing momentarily in the primary 
lies about itself, a magnetic field of force, which, 
other coil of wire is placed within it. wilh i 
to -^hat of the primary coil induces in this 

, .current, as it is termed. 
, or induced current is 
3nal , to the number of 

to the IJumber of turns in 
ary winding. Thus, if the 
)U contains 100 turns of 
the secondary 50.000 
>n if 10 vohs passes 
__ie primary, the second- ■ 
n^ have 50,000 divided by 
S times 10 volts, or 5000 
if^ed in it. This is suffi- 
^^ to leap a gap in ordi- 
, one-quarter of an inch 

alon of the coil at make 
'[ of (he primary current 
ps best explained by the 
> shown in Pigs. 4 and 5. 

J Fig. 4, the din * 
\AaaeA current in thi 
ililr S, is opposile t 
. cf the primary ci 
The half wave of the 

■ the primary circi. , „ 

I. veiy high value, and is 

• the "inverse current." It is very undesirable in 
[. X-Ray tubes, tending to blacken the tubes. In 
r faradic induction coils, it is always present, but 
rf.a weak character, the secondary current of these 
often referred to as positive or negative currents. 
(de lest paper will show a predominating polarity. 
rftjr of the secondary current is readily reversed 
I reversint; the primary current. The relation of 
jc or make current of ihe secondary is Ki:apt\ica.ll"j 
\ Fig. 6B. The strongest haU Viavt, \\\-4\. tc^mVi.- 




;rfnt C^ 



IF., 

frreaJ 



iJemg the primary circuit i: 



albes 




._._ primary tnagnciizinK curreoi. aa shown by 
Ig. 5. The potenlial value of ihe seconda " 
tEultant from breaking the primary ciretdtA 

* The space f ' -m 



tlie secoiujarj'. C, 
is during the in- 
terval when the 
t ot the vi- 



r 



Xl 



ciirrcn!, the spark 

form being more 
peaked, like that 
in Ftg. 7, owtTiff 
to the quickness 
of breaking the 
primary circuit, 
which ts here aid- 
ed by the con- 
denser shunted 
across the vibrator. Here A, A, are Ihe suddenly ! 
Be'condary half waves of a spark coil at break of ] 
circuit; atid B, B. are induced half waves produced a 
of primary circuit. The dotted lines show the priinfl 
rent. In most cases, when the spark gap is oi afay 
ciable length, the "break induced" half waves, which' 
either positive of negative, according to the polaritji 
primary current, are the ones leaping the gap; the 
''R" half MiaVps nf inverse current, not being able to 1 
gap. In such an event, th( 
takes on a certain polarity, as 
evident; but if the gap is she 
both "A" and "B" half WOT 
ceed in leaping it, then the i 
formed of an unsymelrical, pn 
alternating current. A regwi 
soidial alternating current ■ 
whose both half waves, posit 
negative, are equal or nearly 
magnitude and duration. 

The polarity of spark « 

charges can be ascertained by 

ing two fine iron wires to the 

dary terminals. The wire rei 

cold is the positive one, whi1« 

becoming hot is the negative ; 

For operating spark coila a 

mom efficiency or voltages ov 

alternating or direct' currei 

Gernsback Electrolytic Intern 

a very useful instrument. It I 

of a special metal rod reatin 

porcelam tube, having a slight 

or opening at the bottom. T 

and rod are immersed in an 

lyte or acid solution, and wh 

nected into the primary circut 

it enormous speed, the rate of mi 

reaching several thousand a sees 

1 operation, also inexpensive as to 6 

. .. ,■. Its appearance is seen at Fig, 8. 

volts or 220 volt circuits, a choke coi\ conaisUng^ irfj 

' , wound with severa\ \asei 
J^gnet wire, is best connected i 




teiVe current flowing and blinking the \'-^.ts. 

pf hooldng up the choke coil is shown at Fig. S 

k resulting from the use of the electrolytic interrupter 

1 at Fig. 9A. 

lark coils of the induction type are also widely usee 
ras and gasoline engine ignition. A diagram for connect' 
Bp at '/," spark coil to a single cylinder gasoline engint 
a at Fig. 10. 



fUMS I 




Fie. 9 

standard form of spark coil is depl 

"BuU-Dog" Coil pro- 
1 by the Electro Import- 
Co,, of N. Y. City, and is 
all sizes from K" 
t Up to 12" spark capacity, 
e field of experiment with 
coils is endless, and 
! of the more interesting 
llistnictive examples are 
, below, hut it is hoped 
these will but serve lo p 

the way to more elab- 
and extensive experi- 

It may be said that the bigger thi 
rate and spectacular the experiments. 





yet 



extremely interest- 
ing experiment with 
Kt any spark coil is 
the spark ladder. 
' Two thin iron wires 
are bent as shown 
at Fig. 12. By a lit- 
tle experiment, the 
proper shape of the 
wires will be found, 
when the spark will 
run up the ladder, 
Stop, begin at the 
bottom, etc., repeat- 
ing the performance 
indefinitely. The 
cd air caused by the passage of the spark. Is the reason 
'the Spark tending to rise. Heated air is a better con- 
T than ordinary air. 

Wry pretty experiment with spatV co\\a, \s 'C&a.i ■^.^t-Kw.^ 
Tewing carbon or other filings vipcin a ^\a.s& ^\a\.t. ^^^^ 
E connected to opposite enia o\ "^^^^^H 
^^^1 




of filings- The spark divides np and lakes ._ 

■' a filingi. forming a very striking experimcDt. 
A spark-boa 
easily made" 
amply reward 
builder, as it 1 
tretnety preQ 
ihe dark, -^ 

sparklins 
monds. Ati 
A, is shown 
10 tTtake a r 
spark board. 

This ■ 
but a piece < 
wood well 
lacked, and < 
on the froitf 
with tinfoil. 
on a I cuts 

rp knifi 




ther 



lade IB 



shown dividing up the surface into a large number of 
spark gaps. Using diRereni kinds of metal foil, ftW 
copper, aluminum, etc., gives different colored sparks 
iTig, 13 B, is shown how to construct a spark v/OT^it 
The letters are formed of a narrow strip of tinfoil*] 
continually forward toward the other end of the boO^ 
foil tnay be about %" wide. After gluing it fftat,s 
knife is used to produce minulc spark 
gaps, about ii" to 'A" apart. At oppo- 
siic ends of the word or letters, are at- 
tached the terminals of the spark coil 

The length of spark g'ven by a cer- 
tain coil is always understood to mean 
when measured between needle points. 
When metal spheres are used as elec- 
trodes, the spark cannot leap such long 
gaps, as between needle pomts; for the 
reason ihat Ihe spheres present a greater capacity, and 
of the energy is utilized in charging them. A striking 





of discharge is formed between one baU aivd a 
trade: witli the ball positive t\ic spatV. \s n 
that when the ball ts negalwe. 




Its for ! inch spark between needle points." 
Ittcane square value: lEie majcimum value per I" induc- 
9)1 spark is about 50,000 volts.) 

s spark coil presente a good means of getting rid of 
ir dogs, which prowl around the yard, or for giving a 
urprbc to chicken thieves. One terminal of the second- 
t Uits case, may be grounded or connected to a piece 
iel metaL The olher terminal is carefully insulated 
ed to the object with which the subject is to come 

|t2Ct. 

itO^rSpllS of electrical spark discharges are very beau- 
jiii instmctive. A cut of a discharge is shown at Fig, 
Ordinary photograph plaies are used, (he exposure 



._.; dark. Take a small wide raouth bottle, 

J, it half full with dry pine starch powder or talcum 
Over the mouth of ihe bottle fasten a piece of 




pared saHacc. Tlie pin point is cnnVicc 
Onilary post of Ihe coil. Close anrl open i 



malcinR the epurk, 
the plaie is w ' 
off to clear 

powder and 

regular v , 
Changing the p< 
larity of the met 

t will givi 
t results 
Fig. 14, is the re 
suit of connectin) 
negative pol 




made in a variety t 

upright tubes having pedfestdj 

formed upon thetn, r 

- -aining various itiii.._ 
etc., are illustrated al 
16. These tubes ar 
rily beautifi: 
in the dark, g-lowlng wit 
vari -colored hues. Some 
odd shaped tubes capable 
of giving ol? different col- 
ors are depicted at Fig. 
17. Tliese are highly ex- 
linusled vacuum tubes. 
One of the finest tube) 
made is that seen at Fig. 
IS, which is a tube Co£j 

. ■.! liquid n" 
tures, resulting i 
describable display ot 4 
or, when excited. 

Very little enetgf I 
consumed in Hghtia 
geissler tubes, and i e 
inch spark coil will il'" 
inate 12 to IS tubes 4 
once, depending u^fl 
ihcir size. The avera" 
siie ia 8 or 10 inches ti 
Geiaa\et VvAica ^asHfe t 

made lo Wim a na.Ta^^ 

tube bwGg a r-—-"-^ 




pted chaznber. with metal terminals sealed in both ends. 
aid here, that the metal lead-wire passing thru 
_. _...ist be platinum, as this has the nearest expansion 
bntraction coefficient to glass, 

[ liilest and most entrancing displays for lectut 
icotal study are oblaltied from revolving Geiss 
A small battery motor such as E. I, Co., type 
tfb'e purpose admirably well. 
Blot or attachment for rotating Gcissler lubes 

Here H is a fibre or hard rubber sleeve, serving to 
1 Uip rods R R, supporting the Geissler tube, A 
^ contact drum and brushes are litted to conduct the 
rent to the tube as it revolves. 



THE X-RAY. 

HE so-called XRa^s or Roentgen Rays 
covered by Professor Roentgen of Wurzburg Get 
matiy m 1895 He was at that time expenmenbng 
with electrical dischart,es ■ • ^ 



■ or creating 

m in the ether 
f same as in 

fwith the dii 
_. that these 
I have a very 
fe length and 
jncly high 

Est to wire 

^f fairly lont, 
ta'gtii and lo» 
frequency. 

In conserjuen e 
sf the short V.1 
length of th(, 
X-Rays, thcj ar 
^pable of passing 
through . a great 
number of solid 
Substances, r 
BS readily as light 
waves pass thru 
glass. 

Solid svibstancts 
including metals, 
nbsorb the X-Rays, 
ia proportion to 
their density generally. Lead and ! 
Aluminum offers but slight r " 

ue nearly transparent. Glass and quartz absorb a greater 
portion of the rays. The bones of the human body are fairly 
opaque, while the vital organs and muscles are not so opaque. 
3lie lungs are nearly transparent. 

The following data on the relative transpareoty oi -j 
Ihb substances to the X-Rays may V»e ol m^MtsN. Vc 

^^m "Standard Haadboolt for Eleclrtcal EngVoewa." 



L TRANSPARENCY OF VARIOUS SUBSTANCEM 


^^H^ X-RAV5. ■ 


^^^H 


Garbasso.) 


Spe<-ia<- TroDB- 
OCBrtty, purenc}'- 


Ss^.. 


Mnterlal, Water Water 


UUerlal. Vfalp "• 


Pinewood ....7o.56 ~l.i\ 


Nickel Ifi? 


Waliiul 0.66 I.SO 


Brass 8.70 


Paraffin 0.874 U2 


Cadmium 8.® 


Rubber 0,93 MO 


Copper 8.96 


Wax 0.97 I.IO 


Bismuth 9.82 


Cardboard — 0.80 


Silver I&Si 


Ebonite U4 0.80 


Lead lUft 

Mercury 13W 


Wool-cloth ....— 0,76 


Celluloid — 0.76 


Gold 19.36 


Silk — 0.74 


Platinum 22.07 


Cotton — 0.70 


Liquids. 


Bone 1.9 0.56 


Ether 0.713 


Coke — 0,43 


Petroleum O.S3fi 


Glue - 0.48 


Alcohol ojas 


Sulphur 1,98 0.47 


Oiive Oil .....wis 


Muniinum 2.67 0.38 


Water IJJO'' 


— --Glass 2.60 0.34 


Glycerine 1.26&- 


Tin 7.28 0.118 


Nitric Add ....1.429, 


Zinc 7.20 0.116 


Chloroform ...1.S25 


Iron 7,87 0.101 


Sulphuric Acid. 1.841 


The X-Rays as emitted from 


a tube made for the j 
y are easily rendered 


are invisible to the eye. Ths 


however, by observing them 1 


ru a cardboard screCS* 


with a fluorescent substance such as, Barinm-Ptatinmfl 


ide, Calcium Tungstate, Wille 


mite, etc. These sew 




come luiahl 


(^^^ 


proportion 
k strength a 


'^^^™ V 


X-Rays fallh 








\ of obscrvii 




\ X-Ray view 




1 hand is show 








( hand is pi 




^^ p short distant 




I^T from the to 




|Lj_l between it i 




Fjf fluorescent 








f ally fitted, 




/^ plush, fur, ■■ 




M^9l the smaller i 

^'■'- - ' ■ and cut to' 




face about -( 


PlB. 1. 


The pictta 


hand thrown on the screen, v 


ill show (he bonei ii 


distinctly, owing to the milch 


greater absorbing < 
flesh. The bones ap 


the bones as compared to the 


dark shadow, the thicker the 


jones. the denser th< 
TV through a "fiuro^c 


Aclually the bones are not ae 


wAat is seen is a shadow piety 


re producci^'s <l^(afm 


of the X-Rays into light by the ftuoiea'-iint ^uj^m^g 


screen. 




W. 


104 ^^^H 




c= 



fOie t.._._._.._ . 

A tahe, an-i alio upoa ihe thiclmt** of the tissue and 
_jae througb whi<Ji iher bavc to pa&s. 
IWith large profcssiOBa.1 machiccs. such as nMd tn b 
^~^~^ it varies from a Eew secontls lo H miimte and mote. 
t whetber the "slaagraph~ is of the band, the 
d, the pelvis, ^ic The peUis is one of the hard- 
fcof ihe faoinaii bodjr to skiagraph, as it is so ibtck. 




_,„.^ _s many times higher than that of the flesh C. ._ 
h hence a difference in the shadows cast upon the screen. 
stomach outhue to be discerned from that of the 
jpati and Htsh. 
M A vcr7 good skiagraph of the hand of a lady, with wedding 
i dianiond rines on the finger, is illtutrated at fig. 3. ThU 
X - Ray photograph 
was taken as previ- 
ously explained, the 
length of exposure 
being 10 minutes, dij- 
tance of tube from 
hand, S inches, photo- 
graph plate 8 by 10 
inches. The cuclter 
for ilie tube connisted 
of a IVj inch "Elec- 
tro" spark coil, with 
French double gjirlne 

dvt\amQ «xc\Vwit ' 



2<amp«res. The tube w« & cundard tube designed to 
upemtctl on fruni 1 lo J incli spark coils. In Kcneral, 
Hi or 2 inch coil gives the most satisfactory result!, i 
theilargcr the coil and ttibc. the (|uicker the skiagraph I 
be taken. For surgeons' use a 10 to 12 inch spark coil n 




electrolytic or inercur/ turbine interrupter is generally tl 
ployed. Some hospitals and private practitioners Riake^ 
of as large as 20 inch spark coils, or special transformer H 
utilizing a 120,000 volt high tension transformer, opemB 
from [he alternating current circuit. 

An X-Kay outfit complete, and comprising a special 1 
inch spark coil, X-Ray tube, fluroscope. wire, svritch, b) 
teries, and treatise on X-Kays, is depicted.' 
fig. 4. This enables anyone to experiiQent "f^ 
the wonderful X-Rays, and the price is y 
low, being but $17.75 for the whole outfit ran 
to set up. The wiring diagram for thia nt 
shown at figr. 5. The X-Ray tube is connee 
across the secondary circuit of the spark i 
To prevent puncturing the tube and as sn 
lo the regulation of it, a safety spark gap is 1 
variably left connected across the secondary t~ 
minals of the coil, the length of the gap bef_ 
a little less than the spark length rating of t 

The tube used in this outfit is shown at B 
Ws-8 t. It is an imported tube, and is self reguliitii 

as regards the vacuum. 

In the drawing fig. 7, is outlined the action of the foc 
X-Ray tube. The cathode or negative electrode is at K, and 
of aluminum, concaved so as to direct the torrent of radla 
matter to a concentrated focal point on the anode or ur 
cathode A. At this point of impact on the molecular targi 
the X-Rays are abundantly generated, and as the target 
of platinum, it is not only enabled to withstand almost all 
heat developed, but it also allows no penetration of t' 
X-Rays to its reverse face. 

The X-Rays which are generated at the point of imp! 
on A proceed radially outwards in straight lines in all din 
tions, and as A is placed at an angle of 45 degrees, with tl 
axis of the tube, the X-Rays pass out thru the glass, oppi 
site to the centre of the plate, without encountering any. CO 
siderable opposition. In fig. 7, the direction of the Cdihot 
stream toward the concentrating point on the anode A, 
represented by the doited lines. The direction of the ladl 
tion of X-Rays are represented by dot and dash lines and« 
tend thru the cathode K, but are not drawn in to mak« V 

As the X-Rays pass out thru the glass wall of dw tii 
they produce fiuorescence, usuaUy oi a canaTy yellow or t 
pte-green color, but this varies with tine c\iem:\ca.\ sVia-Aati 
the glass and the degree of exhaustion, ll \% aH.tii\n 
■ ' exactly over the area -which la t*.po%«4 ^ 



siills obtained with ihe focus 



1 

' 1 






the 



(rce of the rays 

almost a point, 
radiographic and 

een effects arc 
rendered 
uch sharper and 
Me detailed, with- 
it the necessity of 
irking with the 
be at some dls- 
nce from the plate. 
A special water- 
oled anode tube 

seen at fig. 8, 
le anode electrode 
ids to heat up and 
i water cools it to 




F^ 






Fie, 7 



e X-Ray tube of standard pattern, the predominant 
governing its behavior under given circumstances 15 
stance offered by it to the passage of the discharge. 
!f the resistance be too high the rays which arc produced 
fe great penetrative power, and pass thro bones almost 
easily as through flesh, producing skiagraphs of flat qual- 
, and wanting in contrast. A tube of too low a resistance 
>duces X-Ray s which have little penetrative power, are 
lost stopped by the flesh, and entirely so by the bones, 
ich appear dead black with no structural detail visible. 
rbere is a wide range for choice between these limits, and 
regular practice, a different degree of exhaustion is era- 
sed for certain classes of work. 

\. low resistance tube of small penetrating power is called 
;, or more usually soft; and one of high resistance with 
]&t penetrating qualities is known as high or hard. The 
■stance tho principally governed by the bulb is also s' 



led by the di 

lie cathode, 



of the cathode and its dis' 






e converge with a 



the c 



e of the 



g. 7, is invariably cup-shaped, and is 
that the rays emanatmg from its sur- 
rtain degree of accuracy upon a point 
:i-cathode or anode electrode surface 



L high resistance results from the use of a small cathode, 
I penetrative rays. A large cathode gives a low resistance 
t soft results. For ordinary work a cathode diameter of 
■ inch is quite suitable. 
kluininutn cathodes are much in vogue, because the Ais- 
Tge would disintegrate particles from any other metal, and 
tribute them all 
r the inner surface 
the bulb, and 
ckening it thereby. 
ace of the 
ctrodc should be 
formly curved, and 
y highly polished. 
he greater the ac- 
employed in 

■the electrodes in 
bulb, the more 
ely the cathode .,,„ a 

mm («e 6e. 7). "«• »■ 

be focused upon a fine point on rtie M\D4fc, a.'RQ w^ ' 
p and detailed will be the sWiagva'sAYS o\ila;\tt*i. 
101 




J 



This is due to the tact that the source of the 1 

nyt Is this point of impact, and from it they procn 
straight radial lines. 

Owing to tlie violent bombardment of the anode aur 
b^ the cathode stream, it tends to get extremely hot, e 
cially if the bombardment ia centered exactly • " 
point, and a hole -would soon be burned thru f 

In practice, however, the concentration is ni 
in ordinary tubes, a compromise being; made J 
sharpness of focus, and the heating effect. Fro_ 
evident, that anything which enables the anode i 
heat rapidly, or to stand a high temperature witlw 
damaged, also allows of a more accurate coscc" 




ic cathode stream, and a greater sharpness in the 4_ 

roduced. Also, such n on -damage able anodes permit ( 
heavier discharge thru the tube and therefore of j 
energy of radiation. 

The anode or anti-cathode as it is sometimes called, cJ 
■sists usually of a small plale of metal fixed opposite to S 
•centre of the cathode, and mounted at an angle of about] 
.degrees with the axis of the tube. 

The X-Rays which are produced radially from it, are L 
directed outwards through the side of the bulb, wberel 
electrodes, thickened glass, or other obstructions are 

The material employed for the construction of the i_ 
lelectrode makes a considerable difference in the efKcicDcj 
the tube, as found by Roentgen. He states that there li 
difference in degree of X-Ray emission, by anodes of diS— 
lent materials, and that at the point of impact of the cacbd 
stream, platinum radiates much more powerfully than ala 
inum; platinum having a very high melting point (3,000 f 
■grecs Fahrenheit), is usually chosen for the material t 
which to make the anode electrode. 

Excellent results have been obtained with iridium 1 
^s a small centre in a disc of plalmutn. 

X-Ray bulbs tend to raise tlieit -vatuu-m ilvet conftJ 
{ vse. and change from a soft low vacuwrn, 1.0 3. \vu^ y 

IflK 



^(titin. There are various methods in vogue for regnlathiK 
jpe vacuum of lubes automatically and otherwise. Three 
Krincipal schemes employed are depicted by the cut fig. 9, 
i A. is represented the chemical regulator, which requires 
"c application of external heat to them, to become operative, 
le sealed glass chamber shown, contains potassium chlor- 
,E or manganese dioxide, which liberates oxygen gas when 
fiealed by the application of a spirit lamp to the outer sur- 
plice of the glass tube. 

. The construction shown at B is like the one just described 
irith. the exception that a plalinum wire is sealed into the 
DDTtion of the tube containing the chemical. Sparks from 
gke exciting apparatus are allowed to pass into the tube thru 
Hie platinum wire, and gas is formed and liberated. The tube 
Ban thus be regenerated at will. 

E'Tbe vacuum regulator illustrated at C, is known as ihf 
tosmotic type." It is comprised of a very small tube, of 
Eetallic Palladium sealed into the side of the X-Ray bulb. 
Tie inner end of the metal tube is open and the outer end 
Uiaed. The tube is covered ordinarily by a glass cap. If 
Sa cap is removed, and the flame of a spirit-lamp applied to 
Ibe closed outer end of the Palladium tube, hydrogen Ions 
bota the interior of the flame will be drawn thru the inter- 
bolecuiar spaces of the heated metal, into ,the exhausted 
K-Ray bulb. This form of regulator has the advantage over 
: proceeding two types, in that the vacuum of the X-Kay 




ulbbiCan be adjusted any numbet'ot twtica, \>>A "CRt t'tw. v 
eg-Omited by the amount of chem'icaX vn 'L\\e "■'^S^^J^^' 
^or tube, which is sealed off air tigVit. - '^^™-^" 



X-Rays present a very enlrancmg field for unUmited 
periment a.nd study, but caution should be observed in i 
jecting the tkin to long exposures of the rays, as they hi 
liroperty o( producing serious sores or growths, whic 
not checked quickly are incurable. Grave effects are cai 
on the trophic nerves, and vital resistance of the siiperf 
tissues of the bgdy, followed in a week or more by >e 
inflammation and necrosis. 

A large X-Ray generator wilh regulating rheostat, 
meter, etc., arc shown in fig. 10. 



LESSON NO. M. 
HIGH FREQUENCY CURRENTS. 

HIGH frequency currents represent the most advBt 
field of electrical experimenlation.and but very fei 
the wonders of these currents, especially when 1 
duced at high potential are known. Hence, & i 
scope is given to the investigator and experimenter, ia 

I- ALTERNATION OR 
< 1/2 -CYCLE. 

+ MAX. CURRENT. 




I MAX-^ 

U-Yeo SECOND - 



+ MAX.CUf^REN 



^ 



— MAX. CURRE 



-'/60 SECOND 



evolving of new laws and pTienomevva,, Itom Te.M«t^ 
^^s most interesting and growing \itan^ ol_t'' 



"B^^*" 



_.]e production of high frequency currentB for experi- 
intal research, is usu^y accomplished by the aid of a 
esia coil, which lakes its name from Nikola Tesla, a. fain- 
ts authority and investigator on this subjecl. Two of the 
incipal sciencista who have given us data and explanations 
■ these currents are Tesla and Elihu Thompson, who in- 
ipendently and simultaneously obtained practically similar 
isults. 

Before delving into the more intricate details concerning 
le arrangement and operation of Tesla coils, Oudin coils, 
c, a few paragraphs will be devoted to the elucidation, ol 
le meaning and scope of high frequency as applied to the 
irrents in question. It may be stated firstly, that high frc' 
iracy currents are invariably oscillatory in Nature,, or 
ternating from positive to negative, and back again, many 
indred times per second. In the diagram, fig. lA, is given 



graphical rep- 

of 



he ^ 

alue, of an or- 
inary alterna- 
ing current, 

or commercial 
iphting, run- 
ling motors. 



IIOV_U 
60S AC 



Wi- 



cycle meaning 
imed for the 



(Vmh 



CohJOEi^SCR 



^ T*tAN»ro»neir 



t 



^imum then 



Fig. 3 



;rred 1 



cries of changes 

Also 60 cycles 

:ion or '/i cycle 



aiteniatioi: 
omprising a cycle. Hence, a 60 cycle cur 
Iso 120 alternations, and the time for thi; 
take place is one sixtieth of a secom 
1 take place in 1 minute. One alteri 
equires for its transmission 1/120 of a seci 
In the curve of fig. 1 B, is depicted a higher tre(}ucncy 
nrrent than the 60 cycle ji " J-- ---J - .... 

1/60 second! 

„iany complete cy- 
les have occurred, 
frequency 



second 
60 




420 



Pie. 2 

s frequency is eqiiivalet 



— , .nis trequency is equivalent tc 
^v «i„.w.n.i".ij (.t. o^tuiid, or also 25,200 c-sc\«, ^et i:wl^^■^^.^5 
.'ommercial lighting currents usuaWv \viivp - 'i'-">*«i*i " 
«W cycles or 7,200 altei ■" 







This explanation is for the nurpotp d{ maknt) 
exact meaning of ihe term high freqntney. In " 
tie*, llie term high frequency is innrijibly «r 
mean a current whose frciiuency is somewhere 
10.000 and 1,000,000 cycles per second. 

When such frequencies as these are employed, msn 
wonderful and hitherto unlookcd for phenomena ap{M 
Among other features which they possess, arc those [> 
mitting of passing it thru or rather over the human bo< 
at a potential of half a million volts, or more. Tcsia, Thoa 
-son and others have often demonstrated the (eoi of paast 
a million volts thru the biidy from hand to hand without t 
periencing the slightest harm or ill feeling, Ordiiiarfly 
m the electrocution of criminals, where low frequency att< 
nliting current, of 60 to 120 cycles is employed, such """' 
tials as 2,000 volts are sufficient to kill the subject. Gc 
but ii to '/i ampere passed thru the heart is sufficiolt 
cause death. With high frequency currents, however, I 
current strength as indicated by a hot-wi 
easily reach several amperes. 

Currents of such frequencies as these, no longer obey tU 
laws governing those of low frequency. For one tnih 
they travel principally over the surface of conductors, a 
thru them; penetrating but a few thousandths of. 
inch, this depending upon the frequency value. The ,bi{ 
lli« frequency, the less the penetration. From this it is 
dent that solid conductors for high frequency currentc 
a waste of material and thin walled or hollow ones of Ii 
diameter, are the best. Stranded conductors arc alwatys ^ 
ter than solid ones of similar capacity, as the formcc 
much greater surface area for a given cross-seed oil, -V^ 
this Is what counts in this case. 




High frequency currents can be produced in several wsm| 
the principal methods being those involving the use of v™ 
Ellhu Thompson generator, a Fessenden high frequent, 
dynamo, or by means of the Tesla disruptive discharge sH 
The latter is the commonest and easiest method of prodtic"" 
j auch currents, and is widely utilized for lecture work, elecl 
therapeutics, exciting X-Ray tubes, etc. 
The general arrangement of the (vmctiotiiA ^atta c 
"'- - --oniplete set is outlined ii\ fig. 2. 



to the diagram. I is au induction or spark coil, 
; not less than 2" spark capacity. T is an air- 
'mer. which serves the purpose of stepping up 
f the current delivered by the secondary of the 
I, to many times its original value. At C is % 
mposed of Leyden jars, or glass plates, coated 




I with tinfoil, A spark gap is placed at S G be- 
electrodes Ihe disruptive discharge of the con- 
^lace. G is the discharge air gap of the Tesia 
y, across which the high frequency oscillations 

of the various parts of the apparatus and 

n is as follows: The induction coil or trans- 

xcited from the battery shown at B, or the regu- 

; and its secondary current at 10,000 volts 

s caused to charge the condens&r C, which 




ary may easily reach i 



miUion and more cycles 
. __. .^ It harmless owing to the 

let" already mentioned. The currents thus pro- 
of course highly damped, i. e., the series of oscilla- 
responding to each cycle of exciting current, dies 
Mro, before the next series of oscillations start, 
quency of the Tesla currents produced obey a cer- 
which is as follows: They vary as the square root 
oduct of the capacity and inductance in the closed 
[, circuilG. The freoutncv m fycXes ^w atcwvi w 
rff—'j:— (n« ^-.,.. e ftii v^ ttve s^^Matt \ciQt <A <fti 



CipacJtjr, mnitiplied by the iniluctiuice; where the t . 
is in microfands, and llie inductance in centimeten,, ^ 
further particulars ste "Wireless Cour»«" chaplerB 17 Ul 
Also •■Consimciion of Induction Coils and Transfof«e«,*'j 
H. W. Sccor. 

Anoiher form of higli frequency transformei 
lensively for eleciro-thcrapculical applications. Lb i 
coiL Its appearance and connections are si^en at j 



I 



seen the bottom of the primary and secondary colli 
joined together. Any Tesia coil becomes an Oudin I 
the primary or heavy wire winding is simply placed 
end o£ the secondary, instead of at the center ; 
The relation of the frequencies and voltages 
readily understood quite probably by inspecting 
seeit that the coils or transfortners do not chanj 
quency in themselves at all but only the voltag* 
dependent upon the relative amount of turns of wire up 
the different coils. (See Lesson No. 4), A cut of a poisciii 
high frequency generator designed by Dr. Frederick Su.-:ii:> 
for electro-therapeutical purposes, is illustrated by fig. 5. 

For experimental 1| 
search a very neat d 
efficient form of TJ 
Iraiisforiner is demq 
ni fig. 6. It is bw!^ 
Ibe welt known ^1 
trical firm. The F 
Importing Co., 
York City, and iL^ 
a very ceasonabt;|| 
in comparison to^ 
wonderfiil resull 
tainable with it. 1 
activity, whgn i 
from a 2" spattCj 
operating on baiCtf 
it takes on the 8^ 
ance displayed iti 
but the life ands 
of the discharge 1 
only be fully apf 
ated by actual obi 
tion, and not frq 
mere black and ■>.. 
print. This coil ig] 
,,,, . , , miia-bly suited 

pflvafe /afcoratory, the School \ect\\Tc p\a\loim, aaS. 




n general. A larger exciting eojl may be employed 

1 lliai mentioned, and of course the effect is greatly en- 

(See the Feb.. 1914., E. E. for a special article on 

Is of Ultra-High Frequency and Potential.") 

■he adjustment of the circuits of Tesla or Oudin coils has 

pe carefully tried out by experiment to attain the maxi- 

I results. The length of the spark gap, the amount of 

Icnser capacity and number of Tesla coil primary turns 

fcirciiit, all have a direct influence upon the final high fre- 

pcy discharge, and 

-> should be care- 

F adjusted simuU 

'f or s 

mbl th< 




given: It may 
1 to state that the 
spectacular re- 
are only obtainable 
high frequency 
leasant shock is expei 



FlE. I 



a good dark room or hall. When 
is to be handled by tlie body, an 
iced if the Tesla spark is allowed 
amp direct to the skin; and a piece of metal held in the 
li or a Geisster tube, or even an incandescent lamp is 
; the brush or spark being absorbed by Ihem, and com- 
licated to the body without shock. Geissler tubes and 
like are very useful tor demonstration, as whenever the 
harge is absorbed thru them they light up brilliantly, 
:ing visible the great activity occurring. Several people 
r be placed in a circle and a Geissler tube placed in the 
da of every couple. When the current is applied to the 
s at the ends of the circle, the Geissler tubes all way 
ind will simultaneously light up, making an impressive 
ct. 



1 Fig. 7 are sho 
:h can be perfor 
At 1, fig. 7 Is : 
ical copper i 



■n a number of interesting experiments 
led with the Tesla coil illustrated in 6g. 
1 experiment requiring the use of two 
, as nearly parallel as possible. When 
apparatus is working in good shape, with the frequency 
If the space (2-4 inches) between the two wires is filled 
t light, while the ends show a heavy brush discharge. 
he experiment seen at 2 is performed by arranging two 
18 of copper wire, and attaching them to the secondary 
ninals of the Tesla coil. A similar arrangement is that 
t 3, but here the inner loop is 30 centimeters in diam- 
(1 inch equals 2J4 cms.), while the larger loop is 80 
imeters in diameter. The space \;)e\'«te'n v\vt tftv.ttW.'fiR. 
: filled with millions oi Sine st"^^. V*^'^^*''^* ^ 
pretty effect. 

V15 




minal of the Tesla secondary is connected to the w 
and the other terminal to the opposite wire name. 
:foiI coatings on the back of the glasses are connected?, 
gether by a. piece of copper wire. When the current '» 
■" ninated. Hard rubber may tw. 




The rotaling wire, 5, at fig. 7, ia vevy amMsmg vq obsei 
The wire must be quite fine, and \Vve Veng'tta ie^tTVftKi ' 
ejEperiment. When of t\ic right. \eng\.\\, i.\vc ■ ' 



ibsetX^ 

1 



I a circle contirually. It if 

■A short piece of thin, cotton 

1 to one terminal of the i 

e vSttet. seen at 6. 

_. ; of the most astounding st 

K)tMncy, high potential 



connected to o 

overcd copper v . 

ill, givea out a beautiful 

vith high 



performed \ 

that known as 1 1 

at 7, fig. 8. A heavy piei 

rod may be bent into a. U-shape as 

id when shunted by a. law voltage lamp bulb, the 

light up brightly; the high frequency current pre- 

' averse the comparatively high resislaiice path 

istead of the low resistance offered by the brass 

. probably similar to lightning effects, ctc^ where 

?n that such high frequency stirges, tend to take the 

: path, irrespective of resistance. For this 

_ g rods are always run in as short and straight a path 

nible, avoiding sharp bends. In the Tesla coil experi- 




r.ia T09la'»"WorldWltelBas" 

Bjent here mentioned, a Leyden jar or other condenser i 
Connected across the secondary coil terminals, with a spark I 
; of the leads going to the copper bar. The ter- j 
Biinals of the 20 volt lamps are tried in different positions, 
until the maximum brightness is obtained. 

■ At 8, Fig. B, is a display oi ^ciTi a^^e^^^'ace, c;^«t.(i SSifc I 
'e^tfifatl Piafitota." Tvi ' ' ' " ■ - ^" »- 



a iVim mela\. 6isc^» a-VawiX V ^.v* 



in 



I^'fwl 



etcr, are connected to th« two atcoadaxj terminals of ll 
Tola TrtDstotmtt. Their cdgea are Krouod thin. Wilfc A 
voltage at a high value, while raya or (breads of Hght k 
out from the edges of the discs, which are sometiines of 
siderahle length. 

Electrical wind, as performed with static machines, JAjH 
reproduceable from the Tesla coil. Us effect is illm" 
9. A small sharp toothed aluminum disc, about! 
thick, is mounted on an axle, having very little frit 
when the current is turned on, the litlle disc wiUi 
high speed, becoming enveloped in sparks. 

An illuminated cone of light is made by having W^ 
ring connected to one terminal of the Teala coil ano 
ball of a the ring diamcler, connected to the other h 
When current is applied the space between the ring ami h 
is filled with multitudinous fine sparks, giving a unique • 
beautiful display. , 

At 11 is depicted Nikola Testa's ideal wireless figs 

I for illumination. Evacuated glass tubes are placed i 
imity to the charged metal plates, connected to a source ^ 
high frequency, high potential electric current. The bi 
»re thus illumined by induction, without any metallic < 
nections whatever being made to them. 
' Just what can be accomplished when large amount 
electrical energy is transformed into high frequency, m; 
I potential form, may be gleaned from the photograph Ot son 
electrical discharges of this nature, at fig. 9. This is Iro 
' some of Tesla'a experiments. The sparks shown were 3 
■ feet long, the potential several billion and the amperage 8d 
] Tesla's laboratory and tower erected some years ago oo Lm, 
• Island, for experimenting with world wave telegrapliy. i 
, depicted at fig. 10. 



LESSON No. 15. 

ELECTROPLATING, 

PART I. 

is the term applied to th: 




the electro-deposition of ii 



E.I.CftNY. 

E. 1 

other metals, or Yi\eta\V\ci\\Y coiXti i 



Common forms of electroplating, well, known I 
r one now, are the familiar nickel plate on various {)_ 
, utenEils. instruments; gold plating and silver plating, 
^employed ill the finer arts, including jewelry, etc., etc. 

estdes these more well known phases of elect ro-depositt OH 
J metals is thai branch formerly lermed galvanoplastic, 
pich has now been abandoned for ihe term electroplaiing, 




J Ihe electrotype process. The several industria 
§ electro-chemistry, including electrical refining and analyz- 
„. ^;ctroplating and electrotyping are now embraced un- 
r the genaral name of ekctro-metailitrgy. 

Electrotyping was originally evolved by De La Rue, in 
36, who observed that in a Daniell's cell, the copper de- 
bited, from the solution upon the copper plalc electrode 
rving as a pole, took the exact impress of the plate, in- 
lying all scratches, indentations, etc., upon it. 
jDuring the year 1839, Jacobi in St. Petersburg, Spencer 
rjjverpool. and Jjrdon iu London, hidependently devel- 
Trf out of this discovery, a method of obtaining by the 
Jctrolysis of copper, impressions in reversed relief, of coil 
moments and stereotype plates, etc. Murray, another i 
ptttgator, made the improvement of using molds of plaster 
Pwax, coated with a film of plumbago in order to provide 
Konduciing surface upon which the deposit could be made. 
making of copper electrotypes is readily affected by 
Bpending a suitable mold in a cell containing a saturated 
Hution of sulphate of copper. Thru the cell a battery cur 
pit is passed, the mold being connected to the cathode c. 
Egative terminal. A copper plate immersed in ihe solution 
I the' ,cell, acts as an anode, or positive terminal. The 
Kpper tnode is gradually dissolved into the solution at a ratle 
: of deposition at the cathode. Utilising 
e of current, is more convenient than ( 
cing the electrotypes in the actual ( ' 
--, except, if it is especially desifjyy™ 
3 process is widelyemploj;g(L.**«rfTne present time to r 
Boduce repouss^l^Snd ceased ornaments, works of art_ n 
c-simile, anJjBprincipally for the purpose of multiplyin" 
ties of ylolTood block cuts for printing. 

; pro^^Wss of forming electrotypes is also sometime 
■ ° " "iing. To metallize a non-conductor, Stich i 

)r rubber, some finely divided metallic powde 

^Seh as bronze powder or pulverized plumbago (graphite) 
dusted over it. Before applying the powder, the article < 
mould may, if necessary, receive a very fine coat of wax. 
Metallizing may also be accomplished by chemically coaling' 
siicb materials as glass, or otVier objerts \qo ^^^?.\\.i; v*,^^ 
treated in the manner usuaHy emu^o^ed m ^^'^^^■'«SS^^ 
I Vitb silver or gold by the ordmatj 0\cm\ca.\ i\V««^t\«.^ 
l.toODzing processes, -^M 



re convenient than p ro-, 
cell in. a DaiikUi-*S-ra 
ifjnurfed tor the purpos 



The following simple experiitieiit is of iiitereai: 
Having procured a brass button, or other stamped ^i 
article with a design in relief, it is well soaked and clttt' 
with methylated spirit lo remove lacquer or grease t 
take a piece of cardboard and, holdxQg ii above a Buit,^ 
gas fiame, but not igniting it, it is sufficiently warm^ 
melt good red sealing wax. The wax may then be ni" 
into a pool on the upper side of the card. An impre 
is now made into the wax, having previously brcsd 
on the surface of the brass button just the saine U 
regular wax sealing. The depth of the impression at ' 
edge need not be anything much below [he centre of 
edge of the button. 




If this has been done suecessfuly. the card is trimnl 
down, a few drops of alcohol are put on the surface of | 
wax mould when fine powdered plumbago is brushed' <. 
it by means of a soft camel's hair brush. The whole si 
face exposed should be thoroughly coated with the plumba.; 
finally brushing off all superfluous material. 



I ■..,... 

^H electrode of the plating cell depicted 
^H slightly and embedded in the sealing m 
^^■^projecting juSt clear of the mold. Ovci 
^^■F^plumbago is brushed lo complete the cot 
^^1 of the mold. The prepared mold, -with 
^^m 'Og, is now to be suspended in the mne 
^K j?&tj>]^ cell. Fig. 1, as shown, utiVvz.m( 



Fig. I, ia 1. 
s, with thcVl 
this point ft,j 

ts plumbai 

..^— ^ -_.„ _.„. ., _„ j,™e\s\A\oT 

mtwa i/ "necessary. Tlie weigiit s\iou\d be \iv4>»\^\ca iJ 



L The setting up of the plating cell (of the "Electco" make) 
l-^doue as follows: 

^•Thc glass jar anil porous cup are washed out, and the 
a of blue stone (vitriol) is emptied into the porous cup, 

9 tlieu filled to within 1J4" of the lop with hot water. 

t boiling water. After letting it cool for ten minutes, Che 
^bttire may be stirred with a wooden stick. Its color should 
ft deep blue. The iiite cylinder electrode is next placed into 
pe- glk.ss jar, and same is filled with a solution consisting of 
meat}' parts water and one part sulphuric acid. The acid 
KliBt always be poured into the water, and not vice versa. 
Hr else the contents of the vessel may be violently ejected 
^to the mixer's face. The porous cup with its solution is 
iced into ihe zinc cylinder, noting that tlie height of the 
tvo solutions are both the same. 




I He object to be plated is attached as seen, to the lower 
Vd of the copper wire held by the adjustable clip, allow- 
o( raising and lowering it. Once the object is attached, 
I lowered into the porous cup and the plating begins. 
1 very good deposit is obtained in from ten to Hfleen 
JoauteSi on metal objects. The deposit, of course, is copper. 
iny metallic object may be coated with it, directions for 
"tearing and cleaning such objects being given fully a little 

^O resfime the subject of metallizing the wax mould with 

i plumbago coating, it is lowered into the cell solution, 

"■■■■I the porous cup. If by chance, the current is too 

[, evidenced by burning of the copper deposit which 

ESta its presence by dark brown smears and marks 

a the edges, which should normally be of pale salmon 

C color, the zinc is suspended a trifle out of the solution. 

t,.wax mould is left in the plating cell for approximately 

jaty-four hours, when it may be removed and stripped. 

%t^a does not occur easily, the wax can be melted off with 

Hjlrt Jieating applied. The electrotype may be cleaned with 

iCtbylated spirit. If any pin holes appear in the deposit, it 

irpractically certain it is due to imperfect depositing of the 

or to the presence of loose plumbago on the surface 

mould. When the process has been successful every 

Uil of the original impression is reproduced exactly. If 
j»«pectmen is to be oreserved. a little chloride of zinc may 
Ej>«ahcd over the hollow back oi ^\\e eXetXro'i-s'^t, V^-«\b.%. 
' Mwly cleaned the surface weW. K sVeet qI <^™\5?? 
mt OB by spreading it over xW svLr^^tt a.w&. ^'»*™ 
(type face downward over a ^wftst-o- K^a ^»"=^*=- *-^ 



which the body of the shell can he llllcd » 
or lead. The following current ilcnsiiy values arei'„ . 
being given in ^mprres per 100 square inches of l__. 
exposed. For copper cleclrolyping from an acid bath *i 
tion, best quality lough deposit 1,5 to 4; good ani tJJ 
deposit, 10 to 25; solid deposit sandy at edges, 2S' 
sandy and granular deposit, 50 to 100. For copptim 
from a cyanide bath, 2 to 3; zinc, for refining, 2 toaP 
1 to 3; gold. 5 to 1; brass, 3 to 3.5; iron (steel fedr 
U; nickel, begin at 9 to 10 and gradually diminish 4 
For copper plating metal articles, such as brass, U 
' the object should first be thoroughly cleaned. _ 7" 
hanging the article in boiling caustic soda solutioi 
to ten minutes, which serves to remove all dirt ai 
from the surface. Rinse the object in cold waterj§ 
then ready for plating. In case the object < 

the plating bath rough with fine holes on the 

most probably dns, lo instiflicient cleaning; and It 4 
rect^Bacd. Brass and iron objects should be ] 
well scrubbed with the hot caustic soda solution to , 
dirt from CTcvices. etc. When the plating deposit J 
made heavy enough, the article can be rinsed in cof 
and dried by rubbing with a piece of flannel, or by f 
" e sawdust. The latter is the method usually e ' 
commercial plating shops. 



Small animals, flowers, lace, etc., are metalliz 
cleansing in meLhylated alcohol and while moist, i 
thoroughly dusted with plumbago, filling all the 
indentations. A wire is then fastened to any paiG_ 
object and plumbagoed to the object to make perfec 
ncctioR. It is then suspended into the porous cup ai 
copper plating begins. Very beautiful and artistic work c 
be accomplished in this manner. A cut of the "Electr 
copper plating outfit is shown at Fig. 2, 

For cleaning up articles preparatory to plating, a pow 
head or buffer head, consisting of an iron standard witll-l 
short shaft threaded to fit nuts at each end, and mcnintd 
with a driving pulley at the centre, as seen in Fig. 3-A, 1 
very useful. The buffing wheels employed for polishlM 
the plated articles are soft and composed of numerous din 
of cotton flannel, sewed in circles and held on the Ijuffl^ 
head spindle by a flange plate and nut, as seen in Fig. 3-9 
Scratch wheels with wooden or wire bristles can also be BtJ* 
onto the buffing head as well as emery wheels, for preparid 
articles for plating. To drive the buffing head swindle, I 
I foot power treadle will be found handy "vl motor yo ^w | 
t at hand. A usual form of toot power Avwt w -*- 
r. J-B. 



r small plating work balltrries «ao be eniptoyed for the 

«'of electrical tttergy. Some form of closed circuit bat- 

f ft itaMntivc, a ,good type being the Gordon primiiry - 

lery «eB. depicted at Fig. 4. These cells give about 7/10 

t <scli, and have enortnous ampere hour capacity, rang- 

,0 several hundred ampere hours in the large sizes. 

e suited to constant load and sufhcient cells can bc! 

J give the desired voltage. For some 

, « pUting dynamo may be more suitable, as when 

er, etc., is available to drive it. A suitable dynamo 

I at Fig. 5. Plating dynamos, as a rule, do not 

(T 6 volts but 15 to 20 amperes in small nnits, and 

Mlierally shunt wound, viz., the field winding is 

multiple with the armature brushes: series 

too apt lo be reversed by back E. M. F. from 

__^_j tank, which acts as a battery. The "Electro" 

f and type "S S" dynamos are suitable. 



t tor c 



ntroUing the 



^gulaiion and can 

[I is connected in 

the plating tank. 

630 n el b\i fifing' 



^ useful variabli 

nt or strength of the plating . . 
ilus rheostat permits ot the finest 
f 2 aniperes for any length ot lime. 
rilh one of the lead wires going 
jparing smooth finished articles o 
_f they are held against it firmly, applying some polish- 
Brougc from time to time to the wheel, Rough surfaces 
(t.be dressed down before attempting to plate them by 
fiAnd grinding on an emery wheel, finishing them on 
latinel wheel with polish rouge. 
bvinE given these details consideration, attention may be 
^d to" the subject of nickel plating. The first part will 




..... „ . : illustratioa. Fig. 7r 

ickel plating set complete, with glass jar for holding 



small nickel plating plai 




. The 



fc-eolution, nickel salts, 1 

a?or plating articles with nicket not over 5 volis is generally 

To supply the current which must be steady. 2 to 4 

□ primary cells may be used, also Crowfoot. Bunsen 'or 

: adaptable. Storage cells form an excellent' 

It supply. The type "S S" 6 voll, 4 !|n)pcfe 

D shown at Fig. S, can also be employed ii dcaijtetf * 

r wheel caft.be utilized 10 drive H wi(\\. T\\e -MitM^ 

itful for drivit\g ihi: poV\*.VTOS>lii 

leel. A wuttr tiiovor AtYwertW 





plant, with battery c 
meter V, and main 
Fig. 10. 

In Ihe glass plating tank, sho 
3r plates are placed in the solut 
These form the "anodes" or positive 
nectsd to the positive pole of the plat 
Fig. 10 diagram. The binding post attached 10 the cer 
of the frame is connected to the negative side of the feeding 
t, and forms the "cathode" o£ the lank, when the arii 
a be plated are connected to it and immersed in the solut 
Small copper wires (18-24) may be used to swing the objects 
from the centre or cathode rod. 

attaches to the 

: plated in the tank. If the a . . _.._ 

anode plate than the other, then the side nearest it will receive 
the heaviest deposit, and vice versa. The object must be spaced 
as equally distant as possible, from both anode plates, anJ in | 
this matter, the shape of the object has much to do with de- ^ 
termining just how it shall be suspended. A little experience 
and reasoning will soon teach the experimenter the best way 
which to arrange a certain article to receive the most even 
deposit. 
The solution filling the plating tank ii 




lade up of the tiicket 



ink) ofwari 

with a wooden sr; 
all the salts have !■■ 
solved, when thv 
tank is filled with n 
tion. The follow:. . 
formulas for nickel pla 
baths with sulphat 



I given above, is widely used for nickel 
may also be employed as a basis :' 
following formula. 
Nickel diloride 
Water 2,2*1 
Dissolve and add: 
tamonium chloride 
''ater enough to make 




, -- ' oi boric acid to nickel plating solutions 

fct WHincnded by Edward Weston in the following proportio 
nVo parts of boric acid to five parts of nickel chloride 
I part of boric acid to three parts of nickel sulphate. 
fToo much alkali in a nickel bath results in a yellow deposit 
WJ-niuch acid gives a non-adherent coat. The bath muat be 
rfectly neutral. It should have a specific gravity of 1.041 to 
. IS6, as measured by a hydrometer. If it is weaker, the bath 
porks slowly; if stronger than specific gravity 1.070, the salts 
Tystalliie on the anodes. The bath should be constantly 
„Wched for changes in its density or specific gravity. 
Articles to be nickel plated are very thoroughly scoured and 
uied. using a stiff scouring brush and pumice powder, having 
[jjt dipped the articles into boiling caustic soda solution for 
n to fifteen minutes. When well cleaned, as above described, 
^ne copper wire is attached, and the object, if of iron or 
Eel, should be dipped in a bath composed of J4-lb. hydro- 
Roric acid per one Ballon water, ucmg a wooden tank fo hold 
T solution. If the article is of brass or copper, they should 
Hiipped in a bath of ^-Ib. cyanide o( potassium per one 
■Ion of water. About two hours' immersion in the plating 
I here' mentioned will srive a good deposit. Iron -«r steel 
i copper plale deposit first, as a base for ni^el ~ 
E'Other plate to inake a first class job. Further details a 
ea in the next chapter, No. 16. At Fig. 11, is illustrated 
eCHiptete hydroelectric plant, comprising a water mo 
[ D. C. dynamo on one bed-plate. This set on 50 to 
i/.-'' TMair. will develop 7 to 



LESSON No. 16. 
ELECTROPLATING. 

PART II. 
It this chapter further details and methods for plating with 
^ous metals such as silver, gold, platinum, Etc., will be dls* 
foregoing section, copper-plating with the , 
EclTo" self-exciting cell combining battery and plating ti 
t covered, as well as nickel-plating. 

i few words are added here, relative to copper plating in 

^ulxr manner, that is. with "an external battery or dyns 

■retit feeding the plating vat. The best potentials or v 

i for different metal depositions are tabulated herein, 

3 copper plating bath to be used for ob- 
B not attacked by sulphuric acid or copper | 
^ate* a good make-up is a solution of cop- 
rwlphate, with one-ienih of its volume of 
Jubfaoric acid. The specific gravity as meas- 
redby a hydrometer, (see Fig, 1), should be 
JIS/u and the bath cold when used. If too 
wa copper sulphate is in the bath, crystals 
n form on the surface of the anode, or 
nfiyc electrode. These crystals, altho quite 
n^Ic, will prevent the current from pass- 
■fc. The bath her 

|3Einc etc. 
Klidfl, such 
' llie exa. 

t solution 



. permissable for plating 
It can be employed for 
js those utilized for electrotyp- 
t formula for the above copper- 
is: Sulphate of copper, 1 lb,; 
I lb.; water, 1 gal. The sulphs 



,., , _ __., , - „. . . - __.„ of copper T, 

t dissolved in hot water, when the remainder of the * 
jr be added cold. Then the sulphuric acid is placed ii 
ijtion. allowiTYg the mixture to cool vjeW VieloTt m^\\-„. ^ 

Ebr plafing copper on zinc, iron, Mc, \\ve soViWaotv ^Vov^ft-Ni^J 
k eopper-cyanide mixture, the proportions \>W\t »^ ' 
125 




■lifff : Carbonate of polash. 6J5 <W9,; cyanide ot i 

lbs.; waier, 3 g«h. Th* cyanide of potassium is <_ 

"ihe major portion o( the w*ter, and the carbonate of t 
in a portioti of it. with the carbonate of polash Ji 
t>o'tloii; add to tho 

'potassium solution. 

'first the copper solu- 

•tion and then tlie pot- 
ash solution, ttioroly 
Etirring the -whole. 
If the solution, on 

'trying out, does not 

(deposit freely, a little 

"'more cyanide or more 
Mrhonate, or both, 
may be added until 
the right effect is ob- 

' twined. 

In plating copper 



, the 




mixtu'" "t *-^ PS'" cent, sulphuric acid, and after rinstng H 
in water, it is dipped into a solution of caustic soda or BOd' 
carbonate, after which it is ready for the plating tai Uatj 
principal use for copper plate on iron is for a base )j 
to deposit a silver, gold or nickel layer. This giv^ 
'durabfe finish, with a smooth even coal. 

For copper plating, the plales forrning the 
electrodes are copper grids of as pure a ijuality « 
In Fig. 2 is shown Ihe method of arranging the copjS 
and articles to be plated in the bath, the sketch beP 
from the top of the plating tank. 

Below i. 

of the usual ] 
employed f 
kinds of elet 
The voltage _ 
epecially adjusi 

give I 





Anadu ^ 1 










;:l 


■ 


. 


i 


















1^1* 


^ Callwdej 

Fig. 3 @ 



most suitable 
and depends upon the J 
5Jze of the plating t ' 
ihe area of the ana 
the strength of the fi. 
tion, and several Otq 
things, and t 
determine the beil i 
purpose by experitnent i | 



|C<>pper---cyanide hath S H 

jCoppCr — acid bath -.-.._ 

Klvtr 

Pold 

Srass 

jlron, steel facing 

INickel on iron, steel, copper, with nickel anodes; 

start deposit at 5 volts, diminishing to i.S tf 

'Nidrt! on iron, steel, copper, with carbon anode.. 

Ni^el on zinc 4.(Md^J 

Platinum 5;0' tl 

For certain purposes, such as wireless telegraph condet 
etc., it is often desirable to deposit a copper coating on | 
For the very best work, the copper or sometimes silver oL, 
be burnt into the glass to minimize blistering under Ji^ 
charging. However, copper platitvg in the ordinarjr ww^ 
fer superior to the common itvetlitod ol pas^.i.tvs tirfcrvV la^^ 

~-£7c<:(rical Englnccr-j Han<lbooV, InlemaHQtia\ TwV'ooot O*. 



Jas$, as there is bound to be air spaces Iqlt belween 
pd (be glass, and at these points, the weak spois develop, 
btil finally the glass plate or jar fails and is punctured by the 
B^ voltage. 

■ The following scheme of depositing a metal plating on glass 
ntes or jars is described by S. Wein in Modern Electrics for 
KiigUBt, 1912. 

^Prepare a mixture of sulphur and oil of spike. (Lavendula 
bika), having it of the consistency of molasse 
Pted solution of chloride of gold in sulphuric » 
mo and evaporate at a gentle heat to the consistency of paint". 
^'After thoroly cleaning the glass surface, paint a thin coating 
mixture on the surface lo be plated, and bake in an 
: furnace, to drive off the sulphur and other volatile 
jredients. The result is a very thin metallic film which 
wigly adheres to the glass surface, which film may be 

mforced by clctiro-plaling With copper, "i the ordinarj 
inner. This makes a very suitable coating for LcydcT! 
bs, and the like. 

, - simpler method is to roughen the surface 

I the glass by means of applying hydro-fluoric acid, sand 
bsting under air pressure, or grinding with emery or car- 
Jffundum dust. The surface after being evenly roughened, 
l^painted with a saturated solution of silver nitrate. Af»<M' 
has dried, the treated surface should be electroplated 

jS^I another scheme differs from the foregoing, only that 

Lpainting the roughened surface of ihe glass, the painting 

jdium is a very thin film of prepared Acheson graphitr '- 

ad of the silver nitrate solution. 

FSilVer plating is an important branch of electro-plating. 

^ticles which are to be silver plated must be carefully pre 

ccd, and should be very s 

■Tie article is first boiled ii 

and dirt from the surface. After 

in-cold water and then dipped in a 

_^_ ric acid and water, and then washed, 

a 100 parts; salt, (sodium chloride), 2 parts; calcined lamp- 
2 parts. After a few seconds they are thoroughly washed 
(ftben immersed in the following bath: Nitric acid {36°). 600 
i; sulphuric acid (66°), 80 parts; salt, (sodiuni.chloride),4parts. 
^After emerging from this treatment, they are well washed 
pd cleansed, when they are dipped in the following quickening 
gtii, tintil the objects appear white on the surface; Water, 
fP parts; Mercuric nitrate. I part; with sufficient sulphui' 
pd to dissolve the mercuric nitrate. The pieces are thi 

ind placed in the plating bath. 
pThe common solution for silver plating is the polassium- 
Bvcr-c^anide mixture. A solution of silver nilra 
^precipitated by the addition of lime water, the 
Bttearing as a brown powder. The precipitate is washed 
■refully and is kept in vessels filled with water. To pre- 
T*e iL bath for the plating tank a quantity of the broiyn 
flie of silver is dissolved in a solution of potassium cya- 
' a distilled v 

I or lead wire, not copper, must be used to suspend 
e articles in the bath, At least 4 inches of space must be. 
anode grid and the object to be plated. 
_ . : acquired a sufficiently heavy coating 
J Bilrer, they are removed from the bath, washed in cold 
^leF, and then with slightly acidulated water, using a little 
piphu rid acid in the water, the silver plated articles are finally 
Koihed and polished by the regular process. 
LGoId plating is accomplished by using a tank hath of eol'^ 
ptassinm cyanide- 154 parts oi gD\d c\i\ox\it Vcw? S\^'i««Si 
f 201X1 parts of pure water. A aepataVt so\\i.\:\'3tv ti'L T^^^i 
|poIassium cyanide in 8000 parts ol s "■ ^" ^^"^ 

157 



ptash to cut all oil, grease 
liUng, the object is rinsed i: 
' — T cent, solution of sulphui 



1 the surface. 
i 10 per cent, solution of c 



sTOiie. T\^«o. 



o solutiong ate mixed ami boiled for lialt an itoiir. ^ 
s used cold. To niaintain its atrpngth. gold chloride ai _ 
cyanide m;i; be added ill equal parts as required^ 




Pig. S. Hov 



laimg Tank 

1 solution the foIlowlIlK^ 



For gilding with a ^ 
iC used: (!) 

Sodium phosphate (crystallized) 600 parts 

Sodlutn bisulphite 100 parts 

Potassiun. ryanide 10 parts 

Gold chloride 12-parts 

The first (1) ia for gold plating silver, copper an 
n copper. The second (Z> is for iron and steei. 

The anode for gold plating is a grid or plate of gold. Tf 1 
bath is too rich in gold, it causes the coating deposited' ta J 
black or red in appearance. If the coating is gray, and t 



nide. The a 




of plat 

The 

platinur 



red for 
apparatus. _._. ^ 
following baib^ 
suitable for (daft 

and its alloys: ' _ 
solve 17 parts ot,Ji 
iuic chloride B 
parts distilled .'., 
T li e n dissolvni 

phosphate in "~ 

parts of distilled water. The solutions are now mixed, f 

a precipitate. Slowly, a solution of 500 parts sodium 

phate in 1,000 parts of water, is added, and the whol~"^' 

boiling; replacing the water lost by evaporation, 

niRonia hanng been boiled away, the solution beconti 

id loses the yellow color it formerly possessed. 



colorless, 
strength is maint 
phate precipitate 
platinum plating 

Sometimes it is 

t small castings, 
metal is of some 
made out of the coppe 
line carbonate solution. 
by weight, of cyanide of poti 




_ bath is employed while hot, 
ined by adding ammonium-piatinuni'J 
as obtained above. The anode plat 
s always platinum. ' 

desired to brass plate certain articles, l_ 
or parts of models or apparatus when i 
other material, A brass solulia 

cyanide bath cited above, by adc 

* prepared by dissolving Zp 

and 1 part of z'~ " ' ~ 



The zinc carbonate solution \a a4AeA t' ._ 

^ cyanide bath until the desired color oS \>Tass 4e?w.v\, \» J 
taiaed. The anode ia of sheet bia 



e platJng on iron, has rapidly developed into a large in- 
f. Commercially, it is referred to as galvanized iron, the 
)g being a protection against nisting. Most of the zinc 
ig processes in vogue in the United States employ 
Ic nnc anodes, while Cowper-Coles, in England, uses in- 
te, (lead), anodes, in an electrolyte containing 35 ounces 
ic sulphate, (Zn SO., 7 H, 0), and 0.1 ounce sulphuric 
(specific gravity at 1.84), per gallon of water, 
■ery good zinc plating solution is obtained, according lo 
Iter, by dissolving 200 grammes pure zinc sulphate, (free 
iron), 40 grammes glauber salt, 10 grammes zinc 
ide, and 0.5 gramme boracic acid, so as to gel 1 liter of 
- - With current densities of 0.005 to 0.02 ampere per 
lentimeter, good dense de- 
p to 0.05 mm. thickness arer**l 
by obtained at temperatures be- ' — 
I 18* and 50' centigrade. The 
Dd of producing the zinc coating 
cctrolysis has the following ad- 
ges over the old dipping process; 
olytically deposited zinc, when 
rly applied, is denser, tougher 
Iform and more resistant 




ctroplating on aluminum is quite 
lit, owing to the thin invisib" 
on the surface, (oxide < 
ixide film), which persistently n 
to he eliminated from the base 
itself. Unless great care and 
li cleansing baths are employed. 
;Oating on aluminum will not 

for any length of time. The film t9 _ 

Idc is best eliminated by using a Fig. fi. 

ie fluoride in the plating bath, a Plater's RheoBtat 
xdfaeres best of all metals to 

ham. Hence, aluminum should always receive a zinc 
ifl first. If gold is lo be plated on aluminum, the gold 
a not be deposited directly upon the zinc, as the gold 
m alloy with the zinc, and apparently disappear. For 
...won, the zinc deposit is best given a copper plating 
iKn the gold plate on top of it. The zinc plating solu- 
las about \% of hydrofluoric acid added to it, or the 
ilent amount of potassium fluoride. Before depositing 
old coaling on the copper plating, the latter should be 
polished, as otherwise a large amount of gold will have 

---^ (Q giyg g[[ even coating. 

he electrolytic removal of 



deposited to give an 
I reverse of electro platin 
Siilic coating from the sur 

carried out as an anodic 
.ly in this field is the del 
lU^ considerable proportions in recei 
pse of the enormous growth of thi 
t formerly only the tin scrap of the 



:icle. This 



i gen- 



The most important 
of tin scrap, which has 

factory, (a 



^terial consisting of sheet iron covered with tin), - 
td; the treatment of tin cans, boxes, etc., which have 
naed, has recently been taken up on a commercial scale. 

they contain many impurities, these must first be very 
ly removed, (carbonized, etc.). See "Standard Electrical 
leers Handbook." 

( electrolytic process in this field is invoked for the 
tet of removing the tin from the iron, so as to get both 
n and iron separate and pure. The iron is sold as scrap 
en hearth steel works, etc., and must therefore be abso- 
' free from tin and in good condition. The process 
g been the most successful on a large scale, is that of 

Goldschmidt, in Essen, Gcrmanv. \v w ^ ^.tt^ci. -vx-a;;- 
wd employs the scrap as anode m ^ so\*iVvcn\ q\ ca'i^'u-'^ 

Recently (1906) detioning with O:v\ot\nc, V»^ tcAwtili. 



Pf * < 



■^T" 



tnlo eompeiition with electrolytic ifelinning. _ 
chlorine ma.y be considered as ai> cicciratytic n 

go far as electrolytic chlorine is employed, whik ^ 

of eUelrotylic dctinning are tin and iron: those Of* 
detinniiig arc tin tectrachloride and iron 
' In large plating establishments, wooden tanks are 
also porcelain bath tubs, in some places. For the hesti 
the electrolyte should be agitaicJ, while plating is goi 
and in some cases tlie articles are moved about, to ms 
deposit as evenly distributed as passible. 

Tl IS imperative that good ventilation be had for the 
ing off of fumes from the cyanide or other acid balhs ai 
ping solutions, for these are strongly poisonous and 
not be permitted to choke up or stagnate the atmospb 
which the plater is working. Wool clothes are the b 
fhey are not attacked by acid. The arrangement oi t 
plating vat, with several anodes, is depicted at FI|^ 
various articles being suspended between any twA 
plates as shown. 

In Fig. 4 is shown a fair arrangement of a small i 
room. The building or room may have ordinary plaate 
wood walls. The floor is best of concrete, or bricks 
wooden slat platforms a couple of inches thick pitu 
front of the tanks and sink. The plating dynamo uid 
to drive it are indicated at P. D. The plating tanks A 
ing the solutions are P. P. Dipping vats are at D, O4 
the sink and drain boards are S., 5. D., and T. is a. taU< 
aind cold water should be piped to all sinks and tanks. 
sible. The floor should drain on a slope from tb« 
tanks, sinks, etc., toward the centre of the room. An 
fan in the wall or upper half of a window, as shows,, pn 
a good draught to suck out the poisonous fumes, Wl 
electro-plater pays for in settling his bills for electr^ 
in renewing his batteries, is the number of kilowitfr 
consumed by him. The amount of work performcf J| 
i. e., the weight of metal plated by him, depends soU'^^ 
the ampere hours, tables of the corresponding electn 
esl equivalent being given In handbooks and platers' | 

Since the electrical energy measured in watt-hoars 
product of the volts and the ampere hours, it is evide 
since there is no chance of saving any part of the "i 
hours" necessary for a certain amount of plating, tli 
possibility of reducing the energy consumption is by l< 
the voltage at the plating tanks by a resistance conttCi 
series with the dynamo and tank. . 

In practice it is usual to lacquer certain plated ftnii 
they are not capable of holding their lustre for any lei 
time. Lacquer can be bought ready lo apply, both c( 
hot lacquer being sold. Hot lacciuer is applied by hcati 
plated object gently and then dipping it in the lacque 
may be applied by means of a brush. Chandeliers, 01 
and numerous other articles dipped or plated are 

to preserve Iheir lustre, after polishing-. White 1 

used on nickel, if applied. Nickel plated parts for «! 
switch contacts should never be lacquerea, as this to 
insulating coating. 



LESSON No. 17. 
bTATIG ELECTRICITY AND STATIC GENERATORS. 



supposed I 




!l 



LL bodies iu the unive. __ ^^ 

electric charge, either negative or positive. The earth 

, itself is charged negative and positively at different 

es, and the strength of the charge varies widely 

charge residing upon 

JU'ious bodies is supposed to be in 
rneiltral state, unless dislurbed. 
[ two dissimilar substances are 
limbed, for example, the neutral 
~i^tion existing on theni is up- 
; or disturbed, and when they 
separated, an excess of elec- 

iea of electricity' exists upon the 
The two independent 

__e then said to be electri- 

ppy charged. This form of elec- 

ITed lo the flow of current from a. 
battery, or dynamo, and hence it 
te been named "static electricity." 
t IB electricity in potential form, 
, nearly all voltage, and but | 

amperage. The body re- 

_J to above, as having the ex- 

of electricity, is known as 

^ IsBeseing the "positive" charge. 

Jnd the one having the deficit of 

Hectricity, the "negative" charge. 

Hence, there are two forms of 

tetic electricity, viz., positive and 

" gative, - As an example, if a dry 

ISS rod is rubbed briskly with a 

silk the glass becomes 

asidrely charged with static elec- 

r,- and will effect an electro- 

,. which is described later on, or it will attract bits of 
, etc. If a stick of sealing wax is rubbed with ' 
3T flannel, the sealing wax becomes negatively charged 
. the cat's skin or flannel positively charged. When 
fi respective positive and negative charges are imparted each 
I % metal body, and these are brought into contact, the 
Uges combine, and the electricity is restored to the neutral 

Bodies charged with positive 

BCtricity are indicated by the 

s -f- mark. Negatively charged 

represented by the 

^ — . Bodies charged 

Ith positive electricity, repel one 

pO^er, b u t attract bodies 

.lAtged with negative electricity. 

I^so bodies possessing a negative 

Jiai^ repel one another, but 

^itdily attract positively charged 

■f^i«S. Hence, like charges repel 

ich other, while unlike charges 

t form of static 
Hebtricity is found in nature, 
Men lightning occurs during 
Ehunder storms. The voltage or 
potential of these discharges thru 
atmosphere is enormous. 
.■obably reaching many milUon 
(■ biUfon. Thundeg. i^itta ;^'9»nA, 




T^ tWO-xosKnv-. 



g| 



"^^^ 



crealed by the passage of a liglttning flash, and 
as tlie noise of a spark discharge (Tom a sUtlic 
induction coil. Soiinil Iravels'al the rale of 1090 fe<tj 

second, in ordinary air, and this explains why h h ihi 
lightning flash is seen first, and, after a few secondl 
noise of the discharge or thunder reaches our ears, 
velocity of lightning, if it approaches the speed of ele" 
travelling over conductors, which it probably tl< 
miles per second. From this it is quite simpli 
the distance between yourself and a lightnii 
roughly. The time expiring between the first gl 
lightning flash and the thunder, expressed in 
multiplied by 1090 feet, gives the distance O' 
thunder has come. 

The generation of static electricity in. small 
laboratory study or ejiperiment, electro-thera] 
poses, X-Rays, etc., is accomplished by the 
electrical machines, and infJuenie machines 
Static generator, belonging to the influence claBS>: 
Frictional static machines are not much used' 
except in small sizes, their principal defect bein^ 
and peculiar conditions surrounding the genera! . 
charges with them. They must have a very cleafij 
work properly. The simplest frictional madiini 
a glass plate, rotating on an axle passing throng) 
and silk covered rubbers pressing against its 
rotates. Suitable combs or forks are provided 
plate to gather the electrical charge. Apparati 
in experimenting with static electricity i 
or condensers, electrophorous, electroscope, etc., i 
ments with these will be described presently. 
electric charge resides upon the surface only of bodtes, 
so a wooden sphere covered with tinfoil, or a hollow 
is every bit as good as a solid one for the purpose. Hi 
tubes are as good as solid rods, likewise. 

A simple and inexpensive device for 
ing an electrostatic charge, is known 
electrophorous. A cut showing 
is shown at Fig. 1. It consists 

called the cake by some, composed of 

sulating material, (non-conducting), sttchJ 
' ebonite, or a compound of resin. The 
cake A, is placed in a metal tray B. A 
metal disc C, termed the cover, and abei 
same size as A. and fitted with an ii 
handle D, finishes the equipment. 

The following manner is employed to ^ 
an electric charge on the elect rophororai 
resin or ebonite disc A, is rubbed brisk^n 
piece of silk or cat's skin, causing the 
LevdlnTar ^^sitme a negative electric charge. N_ 
i^jQen jat. ^^^^j ^^^^ j^^ j^ placed upon the plate A. 
acts by electrostatic induction, to cause it to assume a 
electric charge. The positive charge resides on C, as 
it rests upon A only, and as soon as C is removed fl 
negatively charged plate, it becomes of zero potential, 
sing no charge at all. If while the disc C is resting .ttyi 
it is touched by the finger of the operator, (which is tbe 
as connecting it to earth), the charge residing upon A 
repel negative electricity from C to earth, and atH^ci 
farther amount of positive electricity to the disc C. " " 
fAe finger is removed, the positive cViavge ' 
and rvay be removed if C is \ittcd oH \y3 
[ sulitted handle D. 

132 



tiefal bal/--'^ 


MeM rod-W!^>. 




S/OJJ Jar 




»;!■ 


J^ 


CoaZ/hg 


''i" 7 




M 


M 


Outer mefcr/ 




\\ :']MiillM 


@ 




hf the disc A is of gl; 
JfcthE pins-: hprnmps 

fro 



lurj' oi Lcyden Jata. 

instead of ebonite, and rubbed with 

. sitively cliarged. 

the presence and polarity of static electric 

made of a simple little instrument termed an 

iCtroscope. Tlie electroscope is comprised of a glass vessel 

(Fig, 2, fitted with an insulated top piece E. Through this 

is placed a meial rod R, surmounted with a brass ball K. 

itthe lower end of the metal rod is secured two pieces of 

leaf, hence this type is often referred to as the gold- 

-elcct rose ope. The glass vessel sits in base B, which is 



s of metal. 



1 fol- 



1 of the electroscope 
I body containing a static charge 
t presented to the brass ball K, the gold 
hves within the glass ball will instantly 
■verge or fly apart. It no charge t 
ion the body, the gold leaves will re 
stjonless, and close together. The polar 
r of a certain charge may be found by 
; of the electroscope also. First, a 
ve charge may he given ttie a°^4 f\^. t. 

MVes I.L. This may be accoTi\p\\s\\ei \i!ia™ iw ■w»*"w« 
•■rubbing a glass rod with siW, av\d ^^^eft 
^■^axins the glass rod to the baW on X.Ve cXe.axxc.s'^ov'i ■ 



rge »,^ 
old ^^*s. 

'by ^ 



iiGKative charge is left in tlie rlcctroscope, anil ibe glass n 
taken away from the ball. 
The gold leaves diverge when first charged in the n 

described, due m the ciiargf remaining for quite 



Ihc electroscope. If ' 




Leyden jars are bottle 
being the glass plate, tir 
Jar, owing to its peculia 
taining a charge longest, 
for holiiing siaiJL elci-tri 



negatively charged bo 
approached to the ball of ll__ 
strument. the leaves will 1 
pushed farther apart, but if 
body presented to it i» B 
1y charged, the leaveS- 
lapse. It makes no ( 
which kind of a charge 
the electroscope, but i 
a negative charge canb 
ed to the leaves by . 
ing a stick of sealitig wax li 
ball, having previously ra 
the wax with cat's skin or 6 
nel. The electroscope is a # 
useful and important pieca 
apparatus in the realm of h ^ 
potential or static electricity^ ^ 
sensitive gold leaf electroscc 
will respond to the charged ft 
existing about high void 
wires of transmission lineB, •! 

abling electricians worb^ 
around such wires, to 
whether Ihey are "alive" 
"dead," has been patenttd. 
irms of condensers, other tot 
il and paper, etc. The Lej 
design, has the property of I 
id hence it is most alwa 
clurijes, In wireless ti 
ai-ts. the condenser 
composed of glass pi 
they are more compe 
Leyden jars, and ttl I 
they are almost ^n 
discharged, so a.oy 3 
qtuilities offered by^ 
form of coiide ' ■' 

lUclt great iniportance:i.<J 

III Fig. 3 is illustrat^M 
^emi-scetional view - ofiTiT 
ordinary Leyder _' 
ser, having a glass shell''!. 
bottom. The inside ani'^ 

arc well coated with 
about half way up. B 
oil is a good adhesive foil 
ing the tinfoil stick tothe 
Fig. s. aliho shellac may be ul.__. 

An insulated top of fibre, |j 
rubber or wood holds the metal rod. ball and clia.tn^ 
shown, for making contact with the inner tinfoil coani 
(^n)»(:t with the outer metal coating is easily af^ecttd^l 
coiifse." Typical niunufactured Leyden jars are shown 
Figs. 4 and 5. A discharger for these jars is seen at Fig. l! 

The Leyden jar Is charged from a static machine, c 

frictional or Wimshurst influence ivpe, W \\o\4\vi^ 4* v 

t/ie band, and approaching ihe ba\t on \op ol 'i^^ to T 

^parking distance ot the discharging kno\> ol V\wi UM 

fhe jar Aaa its out«r eoaiing thus Bioun4e4 to ea.tm"fl 

-13& 





coatings together, 
small air gap. If 
■ged thru the body, 
k will be felt. For 
ies of Leyden jars 

: Fig.X 

"ng point about the charge in Laydcn jars or 
.fondensers, is that the charge does not rrtide tipoo the 
. surfaces, but upon the glass or other dielectric sepa- 
ithem. The metal portions serve simply to induce thij 
e or relinquish it upon discharge. This is easilyproved 
cans of a. separable Leyden jar as seen in Fig. 7. The 
first charged, and then its outer and inner metaj coatings 
■ed by insulated hooks. It an electroscope is apph>a,ched 

glass it will be actuated, showing that the charge is on 
.BSB portion of the condenser. Presented to the aietal 

it shows no charge. Reassembled the condenser may 
jcbSrged in the regular. manner. 

.aforementioned, there are two principal classes of static 
Btors: the frictional machine and the influence machine. 
Vimshurst influence machine is widely used, both for ex- 
elital and professional purposes; and so it will be de- 
(d here. The ' 




Influence Macliine is portrayed at Fig. 8. It delivers ft i 
spark under practically all candiiioits, which is quite r« 
" "s ordinarily static machines arc unreliable and t 

■«t unless e 






to generate a c 
Dry. cool weallicr i; 

To resume, tie Win 
charge by the rotation of two s 
directions, the two discs being n 
disc on its outer surface carries 
spaced equally apart. The s 



about f 

their operation. 
Influence machine prodtt 
milar glass discs in qj, 
ounted close together; I 
i number of tinfoil sen 

. e number must be lU 

jacli disc so set that at any given instant U 
sectors on one will be just opposite those on the otll 

Two metal rods called netttrali/ing rods are momUe^ 
lei to the outer surfaces of the two glass discs, T 
the arms carrying tinsel brushes, making contact » 
segments on the discs. The neutralizing rod tuid 
on each side of the generator make connection t 
metrically opposite foil sectors on the glass or ebi 
The two rods on opposite sides of the machine a~ ~ 
angles to each other, or less, up to 60 degrees. 

Rotating the plates causes changing values of ^ 
induction to react between them, and the sectors d 
act inductively to charge those upon the other, - 
current is taken from the plates by collecting com 
a short distance away from the moving plate. T' 
the influence machine, which allows it to charge'* 
without being separately excited from an extCr 
electricity, 
Uerowr In Tube. 




type, the i 
to the collecting comhs, and the outer coatings t 
the jars become charged, resulting in a thicker spai 
at slower intervals between the discharge balls. Thflfl 
mum spark length of the machine is attained without til^. 
Influence static machines include such types as the VotSM 
Holtz, also the Topler-Holtz. 

The polarity of the static machine can b 
observing the electrode terminals. Tiie negative elec 
when in a horizontal position, gives a. sharp hissing 
distinguishing it from the positive electrode which ? 
give any sound. The polarity is easily found by mean 
electroscope, previously described. 

Many amusing and instructive experiments can be' 
formed with the aid of such a mac>\me aa vVie "^AccWti' y' 
Aurst getierator. A number oi pieces ul awa.T^iMs A*— ^an 
J be worked by it or other sialic cbatgea ave iWiis^x^vei^v^fl 
|i% cuts 1 to ^ 

US 



_ is seen a universal stand adaptable to holdioK 

nasler tubes, or other apparatus. Cut 2 shows tlie electric 
■Imes, which are very useful for demonstrating. A spinning 
Uteel is depicted at 3, while a static motor appears at 4. The 
wr-riser which projects upward when connected to one pole 
I ttie machine is seen at 5. 
IdagnetiTation can be done by static electricity in the fol- 
: manner: Form a helix of copper wire separating the 
ind then insulating the whole- Within the helix a hard 
leel bar or needle is placed, and if a few discharges from a 
Wden jar are passed thru the helix, the bar will be found 
I be magnetized. 
Ht should be noted that if a co 
) placed upon an insulated t 
"irge will be accumulated by the 
[ Ta touched with the finger, 
brge, as it is then earthed. 
Be the cut. Fig. 11, is shown the i 
in "cascade," as ii is termed, o 
,Jated stands, such as glass tumblers, and the 
w of the last one is connected to earth. 

\ peculiar manner of producing a static charge is depicted 
"' . 13, where a glass tube, containing mercury, is shaken 
f, and then presented to the ball of an electroscope, 

leaves will diverge. A test tube, containing mercury 

i corked at the open end, will serve well for this experi- 



nser, such as a Leyden ] 
J stand as in Fig. 10, 
; jar, but if its outer co; 



LESSON No. 18. 
ELECTRICAL MEASURING INSTRUMENTS. 

T() measure the degree of strength and quantity, also sev- 
eti other diversified factors, use is made of electrical measur- 
B instruments. The two types most generally employed are 
e voltmeter, for ascertaining the potential strength of a cer- 
Jn current, and the ammeter, which indicates what quantity 
t electricity is passing at a certain point in a circuit. 




Fig. 3. 

st measuring instruments work upon the original gal- 
neter principle, which involves the use of a magnetiied 
B pivotally mounted within a coil of one or more turns 
IJnBulated wire. 

; tangent galvanometer was one of the first electrical 

feasuring instruments developed, and a cut of such a type 

t Fig. 1. It is easily made, comprising a loop of one 

_ _. No. 6 or 8 B. & S. gauge copper wire, made into a 

p having a diameter of 62.8 cm. (24.7 in.), and a e.ii<ivi.TO.- 

jnce of 197.2 cm. (77.7 in."). \\ ^Ve vMVtMmtwX. Ks ■K--i*iSi 

eluUy after the above dimenstona, a-fti -a- «a\N-».ivotat^ 

Kdle. placed upon the pedesta\ (,an oiimat^ '^°'^'^**.J' v 

■t ^^e^ve), a current p( 10 ampwea ^i^asvoa vtWM. ^-w^ , 

UZ 



■J • i" 



will cause ihe needle to deflect over 45 dcsreea of 1 
circular dial (% of the circumference). The compass tuieM 
should be placed at the e>aci center of the coil or looffl 
wire, A mftre adjustable type of this galvanometer is !Ud| 
Iraled at Fig. 2, which has leveling screws provided in l 
base feet, so it can he readily set level. Ordinarily, the c 
is set parallel with the needle, when the needle has act f"" 
north and eoulh, or with the magnetic meridian of the e_ 
Galvanometers as a rule are very delicate and used I 
for deiermining very fine differences of current or vi "" 



^^.-.. 



Fig. 5 
I in Wheatstone Bridge measurements, etc. A type r 
favor to-day for laboratory research, but uiisuited tO i. 
work, is the mirror or reflecting galvanometer, shown ait F 
At G is £t very sensitive galvanometer provided w' ' 
delicately huna: mirror of small size. The mirror is 
peitded on quartz or cocoon silk fibre, Behind a gradi 
stationary scale H, is placed a source of light, L. This 



is allowed to fil 
belojv the scale. 



Vhen a very minute curre 


lit is passed th 


/m/^e/er--^^ 




oppcra/i/S 


rv7 


© 



nometer coil, the mirror, vj\rti -mmute permanent e 
I magnets attached to it, is deRec^ed a. ttifte, a.T\i f 
I the beam of light reflected itom t.\\e mvTTOi \ 

c a relatively large movemenl. over At sca\t ft. 

vety small currents are made to gwc «a*\Vj 1 
32& 



fT^ 



V of the mirror 



r 





principle of the action of a.11 types of electrical 
istrumenls is that all conductors carrying eiecir 
set up a magnetic field of force about themselves, 
_oply proved with the aid of an or- 
iy2S cent pocket compass. In Fig, 
and B, is illustrated the manner of 
it The compass needle is set 
lei with the wire, by moving the 
or by the aid of a small steel § 
ting magnet N 
e the wire passes over the topi 

e compass needle, and a current o£l 
I amperes passes in the direction 1 
e arrow, i. e., from right to left, 

right-handed whirls of magnetic 
ftra produced about the wire, when p. 

td at from the A end. These cause ^^' 

compass needle to deflect as shown, if the north-seeting 
'of the needle points toward the left. If the current 
'U from left to right thru the wire, W, then the needle 
" be deflected just oppositely to the direction indicated 
If the wire W, Fig. 6A, with current passing in same 

on, is placed under the compass needle, then the needle 

: deflecled as shown at B, providing the north-seeking 

of Game is pointing toward the left. The north seeking 
pf Z magnetic compass needle is actually the south pole 
e magnet. The north magnetic pole of the earth, which 
« the geographical north pole, attracts the south mag- 
needle pole as like poles repel, and unlike poles attract 
I galvanometer is to be employed to measure, the quantity 
ictric current In amperes, its coil is wound with heavy 
tr wire, the size depending upon the number of amperes, 
'a measuring in- 
dent is termed an 
';ter providing the 
, over which the 
le swings is suit- 
' graduated and 
rkted in amperes, 

ng the deflection 

ed to as the di 
reading 
The 



Jen from Fig. 7, 
^is is the usual 
lod. It is placed 
ties with the cir- 
liiote citrreot is to b< 




the amnMTEcr ncrOM ^ 

liighly conducting, add 

:sUtance of the «■ 

BO iUai b large 

of the current i_ 
the siiunt, wlulc 
fraction of it pasi 




itaetr. 

, the ehunE 

1/10 and t 

winding 9/U 

* itance, "" 

greater portion 

■ent would _M- 

.shunl,^ while ^^ 

ill portion woti 

the ammete 

it is calibrate 

should be con 

other* " 

edle ■»_ 

. a. fractt 

the actual current iraversing tlie . 

In measuring the intensity of the current or its 1 
the instrument -is connected as in diagram, Fi^. fi.j' 
the coil of the vohmeler or intensity meter, is vm 
and so the coil's resistance is many times higher tw 
of the ammeter. Fine wire is therefore used to m 
coil with. For ordinary voltages not exceeding SOO U 
the voltmeter coil is usually designed to care for tlie p 
along with its resistance coil enclosed within itp cMi 
ordinary voltmeter calibrated to read up to, say, 1^ 
can readily be employed to register voltages much,, 
fhan this, by inserting a proper multiplying coil bl 
with it, as at X, Fig. 8. In these circuits, B repre; 
battery or dynamo supplying current to apparatuSj t 
motors, lamps, etc. 

The multiplying coil for connecting a series with th 
meter is made to have a certain definite ratio of res' 
thus: Suppose i 
ton ISO-volt 'bi" 
Strument is to 
on voltages ^ 
or 600. If tfer 
pHer has tt- re 
of three M 
voltmeter (■# 
here about 
ohms), then tl 
tiplyinjr valtie 
■t. Hence if 
^'6- 12. 45,000 ohms,', 

ance, and tfii 

meter but 15,000 ohms, then when the meter Tegiste 

volts, it would be really reading 4x50 vohs, or W 

If tUc multiplying coil had nine times the resistastc 

voltmeter, then the multiplying factor would be 1^ 

vollmeter reading times 10, would be the real vatuv 

electro-motive force presenL , 

A small type'of pocket measuring instrument calite 

read amperes direct, is shown at Fig. 9. It is also --^" 

read volts, having in this case a winding of higher " 

than in the ammeter. Such an instrument is extre^. 

able for tlectriciana, motorists, and all others havin^i 

to test batteries and the like. When testing dry celli, 

age of new ones shoald be about \.!> \Q\\.a, atid tte^ 

on short-circuit thru the ammeter Itovq 1ft xo "" -^ 

A cut of an "Electro" ammeter sw^ab\t \m —.^ 

ftyitchboirds, battery circuits, etc., \& 'iii.vg!aX»p,- 

IV) 




Is calibrated to read from lo 2S amperes. A similar type 
instrument made lo read volts and having a range of 1 t 

volts, is depicted at Fig. 1], These types operate o.. 

Jgnetic vane principle, which is that form having a soft j 

)n vane motinicd on a pivoted staff, and Buitably arranged I 

ithin a coil of wire 

a action is illuS' 
Ited by Fig. 12, 
here E i; ■ " 



ae, W the _ 



oil of 




.. _, and Z the 
sedle deflecting 

Magnetic plunger 

■ solenoid types gf 

rftmeters and am- 

eters are exten- 

rely used, bnt are 

tt extremely ac- 
In Fig. 13 

, a German 

^Ic, comprising a 
111 of wire, arrang- 

1 to suck into its 

nter a piece of soft iron, which is fastened by \e\ 

;edle Z. A spiral spring F ordinarily holds ihe iron plunger 

) out of tlic coiL 

Instead of causing a needle to be actuated by the iron 
lunger, as just described, some makers simply arrange the 
direct, as in the instrument at 
1g. 14. A cut of its make-up is given here, Fig, IS. A 
oliow tin cylinder, made air-tight, is placed in a glass 
test tube, half-filled with water or akohoL Two wind- 
igs are wound about the 

wer part of the tube, one 

coarse wire for the am- 

■rea and the other a fine 

ire for the volts. 

e used separately. 

An instrument for ■ 
- ■ D. C. circ 



Thes 



._ It is known as the 

hompson inclined coil 
leter. The odd feature o£ 
is the soft iron armature 
, secured to the moving 
nndle F. Two coils for 
iha or amperes are shown 
I this instrument also, but 
cotmnercial work, as 
by the General El 



!.«.- u, t,,^ w^..^.a. .-,...- f^ST TUBE. 

!e cSf. it is invariably pro- OR VIAL-A 

ded with one coil, for _,.,„, .,^ __„, 

Iher volts or amperes, as BINDING POST] 

rument originally 
Biployed and built by Car- 
IWi of England, is the hot 
ire meter. Its principle of 
.tion will be understood by 
roking at the diagram. Fig, 
'. A length of fine plati- 
,m or other wire, E, is sus- 
^nded between the support 
.and adjusting screw A. 
t the center of the plati- 
im wire is fastened & airing or fitv« 




WATER- 



t, Ci, ^W'i.»v\'^^ ^ 



adjustable from the s 




r a sradualtd scale 




needle is ndjusted to rcail 
zero. When a currcni ^^^ 
passed, the plalinun! mrr- 
E tends to heat vp ..rul 
elongates o r Icrigid.'iis, 
I h e degree dtpciniini; 
upon the quantity of cur- 
rent. Alternating and di- 
rect current both give the 
same heating effect so 
that the hot wire meter 
is applicable to measuring 
both kinds of CI '^- 



hot 



litis 



country is employed prin- 
cipally for the measure- 
ment of radiation etirrents 
in wireless stations. It is 
well adapted to this pur< 
pose, owing to the tx- 
treinely high voltage used, 
which is not very easily 
passed thru any form ol 
small coil of wire coniainj 
ing a number of turns, 
Another form of measuring instrument adapted to readi 
high potentials, say, above 5,000 volts, is the Electro-stalS 
Voltmeter. Its arrangement is shown at Fig. 18. The actin 
part is simply two or more segments of metal, one set of th^ 
being mounted on a pivoted staff, to which is secured tbe^ 
dex needle, and the other set stationary. When a high p 

tial current is connected to the respective sets of segn 

they are charged, and the strength of the charge is depend* 
upon the value of the current connected to it. The elcM 



mg ones to i 
around a ccr 
amount, and the; t 
indicates the potendj 
on the scale. prevttAt 
calibrated by tneminf:j 
a standard or by I 
air fiap method. 

The standard 1 
uring instrument 
electrical work, ui jL 
coiizitry. is the Westg 
type, built upon' 
D'Arsonval galva 
meter principle. 
principal parts ^ 
I h e i r functions 
represented at Fig, '] 
A powerful and 
magnetic field 1 
vided by the p 
cnt hardened 
magnet P. This is carefully aged by hitting and boilfn 
hoi water to make its magnetic strength as nearly cota.. 
as possible. Two soft iron po\e piccca, B B. a^e st^tv!;!^ 
the inner sides of tlie magnet poles, to toim a. sjmtu 
_ space. The moving elemeiM-, C, » cwct^m" 
laJi copper bobbin, having a iwimbtt oi tatna e>t 
143 



<^^ V 






,/ 


^^ 




\ c 




1 
1 


M. 


1 

1 


.0 1 • o- 


r'f.y^ 



■wound about it, and their terminals connected to two hair 
Springs at top and bottom o£ the coil. The current to be 
measured is passed from the binding posts T T. ihru Ihe two 
iiair springs, and thence around the coil of wire. A magnetic 
is set up within ihe wire coil, and it tends to move one 
or the other, according to the direction o£ the current, 
iction is similar to that of a motor, with a permanent 
ield magnet, and if a commutator was substituted tor the 
'r springs, the coil woul4 revolve the same as any motor 
irmature. 

Within the moving coll Is secured a soft iron core, to make 
tbe path of the magnetic lines of force from pole piece to pole 

Biece more conducting or permeable. Weston instruments 
ave marked dead-beat qualities, i. e., they come to rest quick- 
y, and do not swing to and fro lo any appreciable extent, 
fhis is accompUshed by the coil of wire being wound on a 
:opper bobbin. Whenever the coil and bobbin riiove, Eddy 
tnts, tending to arrest its motion, are set up in the cop- 
The chief features of the Weslon instruments are their 
■eliability, permanence, dead-beat and portability. 



In direct current circuits, the product of the volts by the 
tcperes gives the energy in watts. An instrument reading 
irect in watts must necessarily combine the action of the 
oltmeter and the ammeter. Such a combined instrument 
UvBtrated diagrammatically by Fig, 20. The fine wire movii 




t of the 



H H. 
rhc two windings 
iroduce independent 
oagnetic fields, and 
he reaction between 
bein is proportional 
g the voltage and 
inperage of the cir- 
tut, or sirice these 
WO quantities repre- 
'tBt (he components 
.f the ■ ■ ■ ■ 



the 



istru- 



_ deflection, 

then correctly cali- 
cated, reads direct in 



icter IS the integratin 




■ditii. woa\.\-Vcftit w\t^•i■t f 



of c\ectT>ta\ EWCTgv cotv^-o.^t^'i'Si.WJ 

nslomer of Electric Light and Pov4« t:o«vli'M».«i. »>■ 



T^mi 



; motor, havine no Iron in it, and wbowl 

i is proportional to the voliage and amperage of duH 

I circuit. U is connected the same as Fig. 20. but the inoriof ■ 

I coil hag a silver bar commulalor, and silver brushes lot con-l 

1 ducting the current to the armature coils. The amatilifrl 




Spindle engages a gear wheel of a train of integrat^ 
and the consumption of current in watt-hours prjj 
hours Is indicated on a row of dials on the front of )& 
ment. The sum of the dials is read monthly, and^l 
traction of successive readings gives the net 
sumed, 



LESSON No. 19. 
PRACTICAL MATHEMATICS. 

THE science of arithmetic or mathematics enters t 
or less into all branches of human endeavor t(?_ 
and the young experimenter and student will do y,_ 
to get a firm grasp on least the elementary print^ 
of this subject. , 

The following paragraphs have been devoted to the J 
planation of the more practical applications of mathef__ 
with a few examples showing their value In everyday | 

The process of evolution and ini 
powers of numbers will first be gone o 

Involution is the process of raising any i 
to a certain power of that number, thus: — 2* m 
4th power or 2 multiplied by itself 4 tim 
equals 16. 

Evolution is the science of evolving or extracting o^fr j 
the equal factors constituting the given number. The sqtlj 
root of a number is one of the two equal factors compoi 
the number, i.e.. suppose. 4^ equals 4X4 or 16, then J 
square root o! 16 is 4. Also 4' equals 64 and the cube ■» 
of 64 is 4. since 4x4X4 is 64. The tu'bc ._ - .. " 
ne of the three equal factors wVicVi vjVvew tci'ifllSa 
!tber produce the number. 



given nuiDM 
ins. 2 to » 
r 2X2X25 



62 



36 



e are several ways of expressing powers and roots, 

lal modes being as follows: — The power of a number 

I 6, for example, may be written ffi or 6 — *, If 6^, it 

1 1 

5X6 or 36, but 6—^ means I over 6— » o 

of ten are much used for various formulae, and a 
method of reading their value at sight is as follows- 
;0« means one with 6 ciphers after it, 109, one with 
rs after it, or 1,000.000,000. 

I to be extracted are generally represented or indicated 
radical sign \/ with the number of the root placed 
e V of the radical, thus; f~*, etc. If no number 
over the radical, then 2 is understood, or the square 
to be taken. ,h 



imes t h e 




— 














the follow- 












.eans the 




ti 


o r square 












power, or 






Again it 
ccur, thus: — 








neaning the 
ot of 46 to 


f,fi 


_@ 



urlh root of a number is found by extracting 
.are root twice, or the square root of the square 
The 6th root may be ascertained by finding the 
root of ihe cube root of the given number. Such 
as 42''8 and high powers arc best found by the use 
■ithms. These require the use of a set of logarithm 
nd no explanations will be given here, as nothing will 
rnplished without them. Suffice it to say that many 
se impossible problems are easily solved by their ap- 
I. Any root, such as 7th, 11th, 17th, etc., is readily 
f logarithms. A set of logarithm tables can be bought 
cents to one dollar, including instructions. They 
) be read from ordinary slide rules, another great 
I those having occasion to use figures much. The 
' slide rule reads to from 3 to 4 places, and hence 
:curate for large figures, but for figures not extending 
:o 6 places, it is very handy and gives the result at 
Jivision and multiplication are quickly performed on 
S well as the extraction of square and cube root, 
ms, trigonometric functions, such as sines, tangents, 

rocess of extracting the square root of a given ti 
s follows:— Suppose the square root of 21?,66S.90; 
blinfl' lipirin hv r\t\intintr nfF fh,- nnmhpr infn erri 



, --o— -J p_ ig ott tne number into groups 

gures each, starting at the decimal point, and pointinK 



lUnd; begin by i)0 



g off th 
Bu*^^ Lavh, Starting at the 
ind right, as shown below. 

-) 21,76,68.90,25 1 466,55 
16 sq. root. 

(a) 86) 576 

516 

(b) 926} 6068 

5556 

(c) 9325) 51290 

46625 

(d) 93305) 466525 

466525 

000000 
-ocedure employed to solve i.\vc a.bQvt \«. '0(C\'6-.— %vwv 
^S the largest even sciuaTt in *,^r^ i^qw^Vci. I-o ««. 
US 



ind poioting^jij 



, viz., 21. Upon reflection, il Is evident t_ 
largest even square in 21 is 16, since 5 times 5 is ZS, 
il must b* 4x4 or 16, The 16 is pm down under t 
and subtraclcd as shown, at the same titne bringing dc 
or the next couplet, of two figures. The square root 
or 4 is placed in ihe quotient, to form the tirst figm 
root wanted, — also 4 tnuhiplied by two or 8 is placed 
10 form the first trial divisor. Then say 8 into 57 t 
times, place ihe_6 in the quotient after the 4, and i 
after the 8 in the divisor (a). Now multiply 86 by 6, 
516. Subtracting leaves a balance of 60, plus 68 brought 
from the dividend. 




(c) is found by multiplying 466 of the quotient, by 2 
equals 932, and 932 into 5129 goes 5 times. Place 5 
quotient and also in the divisor, and multiplying 9325 
gives 4662S, Subtracting we have 466S2S. The trial i 

(d) is arrived at by multiplying 4665 of the quotient b 
or it is 9330. This into 46652 does 5 times. Place S 
quotient, also in the divisor, and multiply; the subti 
being zero, finishes this case. The pointing off of pla 

quotient 




217,668.9025 is 466.55. This is readily proved by sqi^i 
root, i.e., multiplying 466.55 by itself, which will | ' 
dividend. 

The extraction of the cube root is somewhat sintila 
divisors having larger numbers are employed. 

Some of the applications of square root are shown. 1 
Considering the right angteU triangle in Fig. 1, if any* 
the three sides, a, b and c, are given, then the valoei 
third side may be calculated. The slanting side c. c 
hypothenuse, is equal to the square root of t he sg 
base squared plus the altitude squared, or c v" a* 4-^ 



Also 
and again 



-b»-. 




If a perfect Square is to have a cer- 
tain area, lh«n the lenglh of the side 
of the square is foiiitd by entracting 
the square root of the area. For in- 
stance, if a square block of wood was 
to have 144 s(juare inches area, the 
length of the side of an equal square 
having thi s ar ea, would be; 
I 144 or 12 inches 

The following notation is 
used for the formulae given 
here for finding the various 
functions of plane figures: 
D = Large diameter, 
d =^ Small diameter, 
R = Radiii5_ corresponding 

r =: Radius cor- 
■sponding to d. 

p = Perimeter, 
■ circumference, 

S = Area of en- 




prious functions of the circle are 

^^^ f p = »d = 3.l416 X d. 

p = 2 ff r = 6.2832 X r. 
ce I p ^ 2 I "Vr= 3.5449 y a. 
P' 2a -(X a 



2^^1.1284 v/a = -^/4~ 



1-= \ — = ,5642 V 1 




:. 3.1416 ri 
pd 



cle varies as the square of the dJameti 

rcle has 4 times the are^ _ _ 

a given circumft 



igle, suc1\ as s\ter«T\ »\.'?\^ 




3, ia ascertained by the formula: 
The approximate area of an ellipse, such as shown hi 



A - — Dd = 7854Dd; 



I of a 



L. Fie. 4. i 



A - - X tD2 - 

4 
The volume o( a spher 

V = l/i 



d=). 



s given by the expression; 
V =^ I'D IT d^ = .5236 d*. 
The surface of a sphere, or S, is found thus; 

S ^ "■ d2 = 4 .r r*. or 12.5664 n. 
Circles, triangles, etc., are divided up by angles, anZ'l 
angles again sub-divided by degrees, it>inutes and sect 

Sixty seconds make one minute, sixty minutes o 
90 degrees one right-angle or quadrangle, and 360 
complete circumference of a circle. Protractors or 
circles of brass and celluloid are usually employed for 
ing, their edge being finely graduated in degrees, etc, 

If the dividers are set equal to the radius of a circle, '. 
T, then the dividers can be stepped exactly six times B 
the perimeter, or forming a six-sided figure called a h^ 
A five-sided figure, or pentagon, is shown at Fig. 6, 
sided polygon or figure can readily be laid out by tbe 
of the following data; 

Table of Polygonal Angli 
Number Angle Number Angle Number 



of 



5 



60 



of 



of 
sides. 



.12 8-11 I? 



»f 



7 21 3-7 \i 27 9-13 19 1? 

8 4.i 14 25 S-7 20 - 1$ 
The angle at the center refers to the angle at a, Figl' 

means of a protractor graduated in degrees, it is easy _ 
out a polygon having any number of sides, by referrifigr 10 
above table. 

For electrical circuits there are a number of dlfiEi 
formulas applying for various functions, the basic o: 
direct current circuits being Ohm's Law. In expi^sl 
the following notation is generally utilized: E ^ ti 
electro- motive force, I or C ^: current in amperes; 
resistance in ohms. 




Thei 



= R 



Thus having any two quantities, ttift OcvvtA q 



mnj. The watts in a circuit are given by multiplying the 
ilts by the amperes; alto. 

£2 
Walts = E I = CS R = — . 
R 
The horsepower is found by dividing the total watts by 746, 
Ltid the kilowatts is ascertained by dividing the total watts 
ly l.OOO. The coulombs of electricity in a circuit is found 
i^ multiplying the current in amperes by the time of its dura- 
men in seconds, the coulomb being a current of 1 ampere 
passing for one second. The work performed in an electrical 
circuit in Joules equals the product of the volts by the 
femperes by the time in seconds. The joule iS equivalent to 
Iwatt or 1 volt-ampere for 1 second, 

The heat produced in electrical circuits may be calculated 
as follows: The heat in calories equals; 

Heat in calories = P X R X T X .24. 
T being the time in seconds. The heat produced in British 
thermal units (B. T. U.) is: 

Heat in B. T. U. = 1^ X -24 X R X T X .0033. 

The volts loat in a circuit equals the product of the current 
ly the resistance. The resistance of a copper wire increases 
11-IOOths. of one per Cent, for each degree rise in tempera- 
«re Fah., or the degree Fah. constant for copper wire is 

;l. 

The joint resistance of a divided or split circuit, sued as that 
ippearing at Fig. 7, is found as described below. If the circuit 
MS two branches, such as R, and R„ then the joint resistance 
>f the two branches, from A to B, is: 

R,XR. 

Joint R = . 

R. + i4. 

nected on multiple the 



ini R : 



number on multiple 
The joint resistance of sever?! different resistances con- 
iected on multiple is found by taking the reciprocal of the 
:um of the reciprocals of the separate resistances, or con- 
luctances. The conductance of a circuit in ohms, beingthe 
'eciprocal of the 
1 



; The joint resistance of three branched cin 
multiple, as in Fig. 7, is completed from thi 



follows: 

1 
Joint R - - + 

Ri R. 
R. 

And the reciprocal of thi 



unple, let the three resistances have 
i 2 ohms, respectively, then: 



Joint R ^ - 




The rapacity of electrical condensers is approximately c 
puted by the equation: 

(2^48 X K X a\ 
I - 10»: 
t X lO'o / 
Where: C is the capacity tn farads. K is the indnctMty 
the dielectric, taken from table in any text book, a it tr 
active area of dielectric or insulation, coated on both tM 
with charging foil, expressed in sqaare inches, t la ( 
thickness of the dielectric in inches. To ascertain llic Ct 
'BCity in micro-farads {a microfarad is one one-million th bF 
farad), solvc_only that portion of the equation enclosed' 
parenthesis. " 

The joint capacity of several condensers connected on ni 
riple is given by the following equation: 

Total C = C, -f C, -f Q, etc. 
The total or joint capacity of condensers connected in * 
is ascertained thus: 

Total C = — 



The area 1: 
have a certE 
formula: 



square centimeters tor a condenser dielectrk< 
n capacity in micro-farads is deduced by A 






sq. ( 



Where * = 3.1416 or pi. 

D = the thickness dielectric in cm. 

C ^ capacity in micro-faruds. 

K = the induclivity facior. 

105 = 100,000. 

LESSON No. 20. 
"HOW TO MAKE THINGS." 
The young experimenter generally finds himself s 



called upon 
models, altachmenis, eic ■ 
to deal with some of the 



. Fig. 1. The Dtvi 



ike the parts of i 
■ ■ 1 this ■ ■ 



i appan 



■c potent features that <wt( 
prove stumbling blocks "" 
the junior mechanic; such 
laying out work, finishlilE 
drilling and tapping of sere 
holes, etc., etc. 

It may be said that, 
arily, the beginner shtiu 
make it a point to maa 

:es from a rule; using 



art of faying off specific 

scale if possible. 
A good mechanic can lay off work on metal with at 

curacy of at least 1/64, inch, and often 1/100 inch. The 

est working by eye does not usually exceed 1/200 inch. 

finer measurements than this, i. e., in the order of I 

sandths, or ten thousandths of ' 

an instrument known 
mil good machine -work. 

Id Fig. 1 Is seen a pair of dividers, 

ing circles, spacing center marks, i 

shown by the cut, Fig. 2, at A, Its 

it is regularly used for finding d; 

sheat metals, rods, and for innume 

ordinarily reads in thousandths of 
set of graduations around the stem 
'hma" after their inventor, it >s_ i 
le Btxe of nn object, auch as a wii 

', _1B0_ 



which is used ft 

compasses^ if or^ttn 

The micrometer 

pe is a wide one, m 

of wire, twist drii! 

lie other purposes. , 

\nch, hut by a sjtI>E 

i\v poaa'\\i\c to n^c:a« 
Li\ ten VVvQ\iaa.niV\\a oft 



A word about reading the micrometer may r 

we lierc. The adjustable part of the mici _ 

Jefully cut steel screw, hidden inside the barrel the pitch 
(the screw being 40 threads to the inch Hence every time 
It barrel is turned ihrough one revolution it advances or re 
H«S from the anvil or fneasuring on the solid stem by smgle 
feduailons. Every four graduations or 100/1000 of an inch 
■indicated by a longer 
1 by glanc- 

_ — .... figiirr i<i 

P/1000, or 12 i 

., ' 25/1000, or 

W/lOOO. Note that 
n reading this value 

lero mark on the 
jirolving brarel is co- 
fcident with the 
pduated line along 

aOtid stem. Odd 

iing the number on 
f barrel index B coinciding 
:, suppose the barrel is un 
Bee fittigle divisions ^d thi 







vith the stem line. For in- 

._._crewed sufficiently to expose 

. ; No. 7 on the barrel indevB 

site the stern index line. Then the vatUe at the 

Kper reading would be 3 X 25 thousandths (mils)," plus 

ps read on the barrel index, or 75 and 7, which is 82 m.ilB, 

emit being equivalent to 1 thousandth of an inch. If the 

||LUdex had been set BO that the stem index line was mid- 

itween 7 and 8, then it could have been approximated 

mis. plus 7>f,or the reading would be .08^5 inch, the 

— Jfsandths figure being guessed at. 

^c'^teasiest way to lay off work for machining:, drilling, 

K., t^.iron or steel Js to cover it with a coating of chalk, 

fclch ptrmits the lines scribed on the surface with a steel 

niited instrument, so as to be readily seen. A scriber is 

bUy made out of a piece of Stubb's steel,. or drill rod, about 

fto 8 inches long and Ji" thick. After grinding a fairly 

iring point on the ends it can be hardened by heatiitg in 

n flame or other fire, to a red heat and then plunging 

es showing the size, location of holes, etc, are scribed 
Bt on the metal, previously chalked over, as aforementioned, 
\ if on wood, simply by a hard pencil, and all centers of 
pies to be drilled should then be center punched by a 
teel punch. (See Fig. 3.) For measuring the inside 
I a hole, or the exterior diameter of a drill or rod, use is 
^de of outside or inside steel calipers, shown at Fig. 4; 
ing the outside 
. _ . These must be 
mpared with a scale 
' rule after calipering 
[rod or hole. A little Fig. 3. amre Puodli. 

serience with these 

[lipers, which are employed in all machine shops for _ 

jg the diameter of shafts, journal boxes, etc., will enable the 
Eateur to caliper quite closely. Some machinists can discern 
IdifFerencc of a few riiousandths by m^ans of these caliper: 
lit for very accurate work micrometers are invariably usee 
JFor cutting off small portions of soft iron and other odd 
Iprk the hack saw, Fig. 5. using hardened saw bladi 
1 to 12" long, is the usual tool employed, la xhnr^ 'a V-tiq 
mch pressure should not be e5,C!:\.e4 iovuvw'iti, i^a "i«>t 
fctii, being Irighly tempered, vjiW \jTe'i\s. oft. »N.^Q ^^*- **-^ 
fouJd be kept steady, not wobbUug A. a>» \^ ^^ smi-*iv% " 



1 



A small drill press arrnngcniciil with a hand drill a«U- 
ioT boring smaH hoks ihrough mctala, liber, wood, ric« 
seen at Fig. 6. The substance to he drilled is easily clatdL 
on the bed plate attacbed. Further drilling accea«ori«S i 
illustraled at Fig. 7, "a" to "c" An automatic reciprocate 
ratchet drill for drilling thin sheet metal, leather fiber, 
etc.; is seen at "a," the different size drills being carr 
the handle. A small hand drill with geared hamJl 
capable of drilling 3/16" holes through iron or soft i^ 
depicted at B, while C shows a magazine tool haiiil!' 
chuck clamping any of the tools displayed. 

Tables giving size of iat> drills for various machtnr 
are given in any tool caiafog. The common sizes o\ 
si:rews and taps used are; No. 4, 56; 4, 36; 8, 32; 6, J- 
10. 24; 8. 24: 12. 24; 14. 20; %'~ZQ: etc.; the firel iim 
dicaling the tap number and ilie second numeral tin. 
of threads to the inch pitch. 

Tap numbers each correspond to certain decimal f 
all inch, and can be found in any tap or drill catalog, A i 




ip wrench or holder B. The holder has an adjustable chuck 
iking several sizes of taps. For cutting threads on rods, t 
steel die and holder 



employed. 
"drilling and tap- 
ing cast iron no oil 
required. For 
rorking wrought iron 
oil is always 

any other 
letals require oil for 

filling and tapping 
any considerable 
Rtetit. 

A tUc is essential 
t all shop work, and 
neat one capable of 
eing clamped to a 
ible top is seen at 

ig. la 




A. most 



iefd r 



Fig, 7 B 



fine is the lathe, upon which any shape of wood, fiber and 
I^SS may be turned up, and a good one for the amateur costs 
at little. A pair of heavy scissors, known as tinner's snips, 
^^ very handy for cutting out sections of thin fiber, tm, 
:et iron, etc., not exceeding 1/16" thick. 
For laboratory or shop use. in heating Joints to he soldered, 
razing and innumerable other operations, the Bunsen gas 
ime shown at Fig, 11 is a valuable asset. It uses the regu- 
,r house gas, and by a set of air holes at the base transforms 
le flame into a strong blue one of intense heat, instead of 
e yellowish flame of low heat emitted by the usual tip. 
For driving screws use is made of a plain or ratchet screw 
fiver. A pressure exerted on 
le handle drives the screw or SS^^^S 
amoves it, according to how 
ic mechanism is set by the 
itton on the side of it. This 
a great time saver where 
nany screws have to be 

Wrenches of various kinds 

e used to handle rods, nuts 

id the lilte, a Stilson wrench 

■r handling pipe, etc., being 

!ry useful — also for fitting 

rand tods of any kind. 

Mdriatic acid cut by dropping Fa ha 

JX$ of zinc in it may be em- "' 

oyed as a flux to solder iron with, but for soldering elec- 
rical joints on copper wires it should never be used, only the 
-acid fluxes such as rosin, being permissible. 



Joy 




Fig. 9 

Thread tut 

Die and Uoldei 



L 




Tig. 12 (Ifpicis a speed counter for taking the S|>eM' | 



riij. 1-. SpctJ Counter 

of siial'ls, pulleys, etc Thg speed of a helt Aiivt 
shaft is dependent upon tT 
proportion existing; beW ' 
the diameters of tbad 
ind driven pulleySfd 






the 



. thtf 



of t 



pulley in inches __ 
call it B), by thej 
tions per minute i^ 
divided by the 
the pulley A, ir 
result being in 
per minute (R. P. i 
The speed ratio *l 
is found by dividj 
number of teeth \ 
large gear by the J 
riR. 10 of teeih on the 

Bench Vise For example, 

had 100 teeth on it and the smaller one 1, 
ilio of speed wouW be 8 to 1, or the smaller g^^, 
would make eight revolutions to every one of the lar^ 



THE METRIC SYSTEM OF MEASUREI 



Measures of Letigth 



HE 



1093.61 yatdi. c 



Measures of Weight 

le t».>=I!.432«r4 gr. Tra-f. or 0.03J1S "i. Tro; 



or 0.9812 too of 2340 lt„. -. , 

1 erain-0.0648 g., 1 oi. avoir.=2SJ5 g^ 1 lb.=D,4SM Kg.. 1 too J 
O.W72 T., 1 ton Z2« lb».=t.016T., ot 1016 Kg. ^ 

Ucaaurcs of Capacity 

. Liter (1,)=I collie di;r;inietcr=61. 0270515 cubic In., Or 0.0S53 
1.0»7 liquid ()(£., or 0.906 dry ql.. or 0.26417 Amci. e:iI. 
10 Lil<Ti>=l DccHliIcr (Dl.)=a.6417 gal., or 1.13S pk. 
irt n-calilcri=l Bcctnlilet (H1.1=I.837S bu. 
10 [l,^.lolFtcra3f Rilolitrr (Kl,) =61027.0515 cu. In., or JS.J75 hu 
1 LU. iool=2a.3a L, 1 Kallon, Amci.=;l.7BS 1., 1 gotlon, Biil.= 

(Fiai..) 




'tz 



DIAMETER OP WIRE WHICH Vi 





DiuciEUcinUili ^M 




Amp. 


C4.PP0 


AIUD- 


PUi. 


.ilver 


a 


Imn 


J5i 






10 

1 

i 

120 

IS 

i 

IS 

wo 


!:! 

1:1 
il 

ISA 


tag 

M 


S.3 

fl.B 

11 

ii 

1SJ.7 


S.J 

Si 

Is 

i 

sols 

ll 

S:! 


H 

lo:* 
Si 

i 

|i 

130:9 
U0.4 


13 :» 

Sl-S 

11 

11 
1 

iii 

172:2 

1st s 


II 

b:i 
1.0 

1: 

TS.S 

,1 

MS 

ii 

!6S,8 
303:8 


B:i 

330.1 





CHARACTERISTICS OB TIUBBft 







to FKlir^ miiK 



3. multlilv I 



by Aiod divide by #. 



Table of Multiple* 

Diameter of a circle x 3.141G = Circumfer 
Radius of a circle x 6.2831SG => Circumfer 
Square of the radius of a circle x 3. 1416 = , 
Square of the diameter of a circle x O.TSS 

Square of the circumference of a circle x O.ff 
= Area. 

Haif the circumference of a circle x by ball 
diameter = Area. 

Circumlerence of a circle x 0.159156 = 

Square root of the area of a circle x 
Radius. 

Circumference of a circle x 0.31831 = Diai 

Square root of the area of a circle x ' 
Diameter. 

Diameter of a circle x 0.86 = Side of ii 
equilateral triangle. 

Diameter of a circle x 0.7071 = Side c 
ibscribed square. 

Circumference of a circle x 0.226 = Slde-o 
inscribed square. 

Circumference of a circle x 0.282 ='Side 9{ 
equal square. 

Diameter'Of a circle x 0.8862 = Side of a. 
square. 

Base of a triangle x by H the altitude •= A 

Multiplying both diameters and .7854 1' ""' 
= Area of an eclipse. 

Surface of a sphere x by 1-6 of its dismvt 
Solidity, 

Circumference of a apiiere x by il 
Surface. 

Square of the diimeter of a sphere x S.Utl 
Surface. J 

Square of the circumference of aapherexO.^ 
= Surface. 

Cube of the diameter of a sphere x 
Solidity. 

Cube of the radius of a sphere x 4.188^ 
Solidity. 

Cube of the circumference of a sphere x O.OlM 
= Solidity. 

Square root of the surface of a sphere xOJi 
= Diameter. 

Square root of the surface of a spher 
= Circumference. 

Cube root of the solidity of a sphere x IJSi 
= Diameter. 

Cube root of the solidity of a sphere x 3. 
Circumference. 

Radiua of a sphere x 1.1547 — Side ol 

Square root of (1/3 of the square oO 1 
diameter of a sphere := Side of inscribed cul ' 

Area of its base x by 1/3 of its altltuc 
Solidity of a cone or pyramid, whether r 
square or triangular. 

Area of one of its sides x 6 = the surface q 
cube. 

Altitude of trapezoid X HttiftBMTi 
Bides = Area. 



Table of Contents 



ro. 1. 

■ic Bells, Buzzers and Annunciators 3 

ESSON No. 2. 

Primary Batteries and Dry Cells 11 

BSON No. 3. 

Storage Batteries 20 

ftSSON No. 4. 

Rectifiers and Transfonners 30 

^SSON No. 5. 

Small Electric Lighting Plants 38 

^SSON No. 6. 

Electrical Wires and theii* Calculations 47 

^SSON No. 7. 

Telegraph and Telephones 59 

^SSON No. 8. 

Dynamos and Motors .,.,...,■,, 

^SSON No. Q. 

Switches, Burglar Alarms, and miscellaneous 

connections 75 

^SSON No. 10. 

Experimental Electro-Physics 83 

^SSON No. 11. 

Electro-Therapeutics 69 

£SSON No, 12. 

Induction Coils and Geissler Tubes 96 

LESSON No. 13. 

The X-Ray 103 

ESSON No. 14. 

High Frenquency Currents (Tesla Transformer 

Experiments, etc.) 110 

KSSON No. 15. 

Electroplating, Part I. 118 

' LESSON No. 16. 

Electroplating, Part II 125 

I LESSON No. 17. 

• Static Electricity and Static Generators 131 

I LESSON No. 18. 

■ Electrical Measuring Instruments 137 

» LESSON No. 19. 

jL Practical Mathematics . . , - 144 

PlESSON No. 20. 

W- How to make things. (The XJst ol "Raw ■^a.\«\.'^ Vft 

ErSEFUL INFORMATION 






TWO REMARKABLE BOOKS 

How to M«ke Vfti 
Receiving App«t^ 



How to Make Wireleu 

Apparatu*. 
Thi* bo oil -;ii 




.ter Publishin 

SEND POSTAL FOR FREE SAMPLE COP" 
FOR SALE ON ALL NEWS STANDS ,^ 



Experimenter PubliaiVans Co.,Vcv 



1