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Dunwoody, 705
Dynamo, 550
Dynamotor, 605
Dyne, 11
E. M. F., absolute unit of, 426, 537

counter, 297, 593
in motor, 593, 594

; : power of motor proportional to,

594
reading of voltmeter across, 595

depends on rate of cutting of lines
of force, 425

induced at make and break, 437

measurement by voltmeter, 461

of cells, 200

measurement of, 329

of generator, 578

of rotating coil, 552

power, 617

produced by cutting lines of force,
425

reactive, 619

thermo-electric, 528

units of, 537
E. M. F.s, alternating, composition

of, 611

Earth a magnet, 116
Earth's magnetic poles, location of,

168

Earth's magnetism, theories of, 181
Earth's poles misnamed, 117
Eddy current, 428
Edison, 504

Edison-Lalande cell, 208
Edison storage battery, 250

advantages and disadvantages, 253

charging, 252

reactions, 251
Effect of points, 42, 43
Effects of electric current, 215, 444
Efficiency of arc lights, 524

of incandescent lamp, 512

of mercury vapor lamp, 527

of motors, 596

of transformers, 649



Elasticity, electric, 691
Electric arc, 485

attraction and repulsion explained,
30

laws of, 24
bells, 410

capacity, 45, 79, 83, 88, 95
charge, 18

cause of movement, 69
current, 215

effects of, 215

magnetization by, 164

mechanical production of, 423

work done by, 476
density, 692
diagrams, 51
elasticity, 691
field, 57, 58, 59, 61, 65, 66

effect on cathode rays, 674

graphic representation of, 61

intensity of, 58, 61

unit, 58, 61
force, 54, 55, 58, 75

variation with charges, 54

variation with intervening medi-
um, 55, 58

furnace, 486, 497, 490, 491
fuze, 483

heating of wires, 480, 481
light, 503

lines of force, 60, 61
pendulum, 22
potential, 70, 72, 73, 74, 75, 83

analogues of, 70

how measured, 72
power, absolute unit of, 49

commercial unit of, 496

expression for, 494

measurement of, 497, 498

practical unit of, 496
primer, 483
repulsion, 22
resonance, 63
telegraph, 411
waves, 690, 694

length of, 696

velocity of propagation, 693, 694
welding, 484



INDEX.



583



Electric whirl, 44

wind, 42, 44, 48, 49, 50
work, commercial unit of, 496
Electrical effects used in measure-
ments, 444, 445, 446
energy, source of in cell, 192
machines, 46, 47, 48, 49, 50

classes of, 550

transmission of power, 501, 502
Electricity, atomic character of, 280,

685

origin of name, 12
static, 14
theories of, 27
two kinds, 26
unit quantity of, 56
Electrification, all bodies susceptible

of, 21

by influence, 28
resinous, 23
two kinds of, 23
vitreous, 23
Electro-chemical classification of the

elements, 225
Electro-chemical effect standard for

measurements, 448
unsuited for commercial measure-
ments, 451
Electro-chemical equivalent defined,

231

Electro-chemical rectifier, 653
Electro-dynamics, 360
Electro-dynamometer, measurement

of power by, 498
Siemen's, 383
Weber's, 382
Electro-magnet, 403
lifting weights by, 409
rule for polarity, 404
shape of, 407
use of, 408
value of, 405

Electro-magnetic effect used in meas-
urements, 452, 453

Electro-magnetic field, energy ex-
pended upon, 359
inertia of, 418



Electro-magnetic induction explained,

419, 420

Electro-magnetic inertia, 418
Electro-magnetic theory of light, 548,

690, 694

Electro-magnetic intensity, 535
Electro-magnetic units, primary, 538
Electro-mechanics, 549
Electro-static units, 535
Electrode, 220

Electrolysis, applications of, 233, 234,
235

Faraday's terminology of, 220

of a base, 223

of fused compound, 222

of a salt, 224

of water, 219

substances subject to, 221
Electrolyte, 193, 220
Electrolytes and non-electrolytes, 275
Electrolytes, measurement of resist-
ance of, 327
Electrolytic cell, 220

detector of wireless, 705
Electrolytic dissociation, extensive

scope of theory, 281
Electrolytic properties depend upon

ionization, 276
Electrometer, attracted disc, 101, 102

quadrant, 103, 104
Electrometers, principle of, 100
Electro-motive force, 76, 77, 78 (see
E. M. F.)

practical unit of, 77
Electrons, 280, 672, 685
Electrophorus, 35
Electroplating, 234
Electropoion fluid, 205
Electroscope, 25

gold leaf, 34, 680
Electrostatic measurements, 98
Electrotyping, 235

Elements, electro-chemical classifica-
tion of, 225

magnetic, 175
variation of, r !76

of a cell, 193, 194

of a secondary cell, 238



584



INDEX.



Enclosed arc, 521

Energy, electrical, source of in cell, 192
expended upon an electro-magnetic

field, 359

loss due to hysteresis, 399
of a condenser, 97

Equality of current at every cross sec-
tion of circuit, 229
Equation, Helmholtz's, 436
Equipotential surface, 71, 72
Equivalent, electro-chemical defined,

231

^rg, 11

Essential parts of D. C. generator, 560
Ewing, 153, 359, 399
Ewing's theory of magnetism, 153, 359
Exceptions to Van't Hoff's generaliza-
tion, 267

Excitation of field magnets, 562
Exciter, 637, 656

Explanation of motion of motor, 591
Expression for electric power, 494
for inductance of coil, 435
for permeability, 392
External characteristic, 585
Fables of ancients concerning mag-
nets, 107

Factor, power, 635
Farad, 95
Faraday, 31, 38, 55, 91, 122, 181, 220,

226, 230, 416, 417
Faraday dark space, 670
Faraday's discovery of induction, 416,

417

first law, 226
ring transformer, 431
second law; 230

terminology of electrolysis, 220
Feddersen's experiment with revolv-
ing mirror, 688
Fessenden, 705

Field at center of circular coil, 354
electric, 57, 58, 59, 61, 65, 66
direction of, 59, 61
effect on cathode rays, 674
graphic representation of, 61
intensity of, 58
near uniformly-charged plane, 66



near uniformly-charged sphere, 65
unit, 58

Field, electro-magnetic, energy ex-
pended upon, 359
inertia of, 418

intensity of, about a straight con-
ductor, 353
Field, magnetic, about a wire carrying

a current, 346
direction of, 347, 348
defined, 134
determination of strength of, 148,

149, 150
direction of, 135
effect on cathode rays, 673
effect on positive column, 669
graphic representation of intensity

of, 145

intensity of, 136

Field of electrical machines, 143, 561
of generator, 561
of solenoid, effect of material of core

upon, 390

variation with current, 389
on axis of circular coil, 354
on axis of solenoid, 387
rotary, production of, 664 [147
Fields, magnetic, comparison of, 146,

compounding, 141
Field coils, 561
Field control, 564
Field excitation of alternators, 673
Field magnets, 561

excitation of, 562, 673
Filament, carbon, 505
Flaming arc, 522
Fleming, 292

Flow of current, direction of, 217
Fluoroscope, 678
Flux, calculation of, 401
law of maximum, 144
magnetic, 142
Focusing tube, 678
Force, coercive, 398
electric, 75

variation with charges, 54
variation with intervening me-
dium, 55, 58



INDEX.



585



Force, electric lines of, 60, 63, 64
from unit charge, 63

electromotive, 76, 77, 78 (see E. M.
F.)

exerted between conductors carry-
ing currents, 361, 362

exerted by field upon conductor
carrying a current, 356

exerted on internal point of charged
body, 67

magneto-motive, 400

tubes of, 62

unit of, 11

Forces, magnetic, measurement of, 127
Formula, dimensional, of resistance,

540

Formulae, dimensional, 539, 547
Foucault, 429, 515
Foucault's currents, 429
Franklin, 27, 43, 86
Franklin's fulminating pane, 86

theory of electricity, 27
Free charge, 33

Free ions, demonstration of, 272
Free magnetism, 142
Frequency, 608

critical, 631

Frictional machines, 46, 47, 48
Furnace, electric, 486, 487, 490, 491

induction, 491

Moissan's, 487
Fuse, 306, 481

Fused compound, electrolysis of, 222
Fuze, electric, 483
Galvani, 185
Galvani's discovery, 185
Galvanometer, ballistic, 384

calibration of, 454

D'Arsonval, 378

defined, 372

mirror, 377

reflecting, 378

sine, 376

suspended coil, 378

tangent, 373, 546
Galvanometer constant, 374
Galvanometer shunts, need of, 380



Galvanoscope defined, 363

increase of sensitiveness, 364

methods of weakening controlling

force of, 366
Gambey, 428
Gamma rays, 679
Gases, conductivity of, 667, 680

ionization of, 681
Gaseous pressure, laws of variation of,

256

Gauges, wire, 295
Gauss, 11, 64, 148
Gauss' theorem, 64
Geissler tube, 670
Generator, adaptation to work, 582

and motor identical, 590

calculation of E. M. F., 578

compound, 563, 588

ring wound, 569

series, 563, 582

characteristic of, 585

shunt wound, 563, 582
characteristic of, 587
Generators, 423, 550, 560, 561, 563

classes of D. C., 563

coupling of, 581

used in wireless telegraphy, 701
Gilbert, 12, 108, 110, 116, 117, 121,

156, 158, 159, 168
Gold leaf electroscope, 34, 680
Gram, 8

Gravity cell, 207
Gray, Stephen, 19
Grid, 239

Grotthus' theory, 274
Grouping, mesh, 646

of cells, 334

of incandescent lamps, 514

of storage battery plates, 243

star, 647
Grove's cell, 203
Hauy's method, 366, 367
Heat, dissociation by, 258

effect on magnetization, 158

unit of, 11, 478

Heating effect, laws of, 477, 478
Heating effect of current, localizing,
482



586



INDEX.



Heating, electric, of wires, 480, 481

Hefner, the, 509

Helmholtz, 280

Helmholtz's equation, 436

Henry, the, 433, 434

Henry, Professor, 403, 686

Henry's theory of oscillatory discharge

of condenser, 686
Hertz, 694, 695, 696, 697, 698
Hertz's confirmation of Maxwell's
theory, 694, 695

oscillator, 694, 699

resonator, 694
High potential, 666
High resistance, measurement of, 326
Hopkinson, 392
Holtz's influence machine, 50
Horse power, 494
Hot wire instruments, 463, 702
Hysteresis, 396

energy loss due to, 399
Impedance, 620
Incandescent lamp, 504

control of light of, 513

efficiency of, 512

life of, 511

Incandescent lamps, grouping of, 514
Inclination, magnetic, 171
Inclined coil instruments, 471
Increase in number of coils of gener-
ator, 558
Increase in number of turns of coil of

generator, 557
Increase of sensitiveness of galvano-

scopes, 364

Indicating wattmeter, 499
Indication of charge of storage bat-
tery, 246
Induced charge, amount of, 31

distribution of, 29
Induced charges, separation of, 32
Induced E. M. F. at make and break,
437

rule for direction of, 421, 422
Inductance, 434, 615, 619

and resistance contrasted, 616
effect of alternating E. M. F., 617
in parallel, 624



Inductance and resistance in series,

623
Inductance, resistance and capacity,

630

Inductance of coil, expression for, 435
Induction, electro-static, 28, 30
Induction, electro-magnetic, explained,
419, 420

Faraday's discovery of, 416, 417

magnetic, takes place through space,
119

magnetization by, 118

self, 432, 614

measure of, 433
Induction coil, 438

use of condenser with, 439
Induction furnace, 491
Induction motor, 428, 662, 663, 664,

665

Inductive coupling, 701
Inductive reactance, 619
Inductor, 560, 569
Inductor alternator, 640, 643
Inertia, electro-magnetic, 418
Influence, electrification by, 28
Influence machines, 46, 49, 50
Instruments, hot wire, 463

inclined coil, 471

moving iron, 464
Integrating wattmeter, 500
Intensity, magnetic, 174

of electric field, 58, 61

of field about a straight conductor,
353

of force between conductors carry-
ing current, 362
Internal characteristic, 585
Internal resistance of cells, 294

measurement of, 328
International ohm, 291
International volt, 212
Interrupter, 410, 438
Intrinsic magnetism, 142
Inverse squares, experimental proof
of law, 131, 132

law of, 53

Inversion, thermo-electric, 529
Investigations of Volta, 186



INDEX.



587



lonization, 268

electrolytic properties depend upon,
276

how it takes place, 270

incomplete, 271

of gases, 681

why it takes place in solutions, 269
Ions, 220, 681

free, demonstration of, 272

not from same molecule, 273
Iron-clad magnet, 409
Iron furnace, electric, 490
Isoclinic chart and lines, 173
Isodynamic chart and lines, 174
Isogonic chart and lines, 170
Jars, unit, 99
Joint resistance, 293
Joule, 477, 478
Joule, the, 478
Joule's law, 478, 479
Kelvin, Lord, 102, 103, 377, 529, 531,

687

Kirchoff's laws, 303, 304
Lag, angle of, 609
Laminated magnets, 166
Lamp, arc, 515

constant current, 520

constant potential, 519

magnetite, 523
Lamp, incandescent, 504

control of light, 513

efficiency of, 512

life of, 511

manufacture of, 506
Lamp, mercury vapor, 527

Nernst, 508

tantalum, 507

tungsten, 507, 512

Lamps, incandescent, grouping of, 514
Lamps, luminous vapor, 525, 526, 527
Lap winding, 575
Laplace, 353, 361
Law, Avogadro's, 256

Charles', 256

Coulomb's second, 128, 133

Faraday's first, 226

Faraday's second, 230

Joule's, 478, 479



Law, Laplace's, 361

Lenz's, 430

Mariotte's, 256
osmotic pressure follows, 264

Maxwell's, 144, 371, 377, 467, 470,
471, 591

of bifilar suspensions, 127

of inverse squares, 53

experimental proof of, 131, 132

of magnetic circuit, 400

of maximum flux, 144

of torsion, 52, 127

Ohm's, 297, 299, 307, 427, 538

sine, 147

tangent, 146
Laws, Kirchoff's, 303, 304

of heating effect, 477, 478

of resistance, 285, 286, 287, 288, 289

of variation of gaseous pressure, 256
Lead, angle of, 570, 609
Lead batteries, care of, 248

objections to, 249

troubles of, 247
Leclanche cell, 209
Left hand rule for direction of motion

of current, 352
Lenard rays, 677, 680
Length, standard of, 4

unit of, 7

Length of electric waves, 696
Lenz's law, 430
Leyden jar, 85, 86, 87, 103

Feddersen's proof of oscillatory dis-
charge, 688

invention of, 84

oscillatory discharge of, 686, 689

Thomson's proof of oscillatory dis-
charge, 687

Lichtenberg's figures, 36
Life of incandescent lamp, 511
Light, electric, 503
Lifting power of magnets, 124
Lightning rod, 43
Lines, isoclinic, 173

isodynamic, 174

isogonic, 170
Lines of force, cutting of, 424, 425

electric, 60, 61, 63, 64



588



INDEX.



Lines of force, from unit charge, 63

magnetic, 137

method of mapping, 138, 139,

141
pass preferably through magnetic

substances, 143
properties of, 142, 143
Local action, 196

remedy for, 197
Localizing heating effect of current,

482
Location of earth's magnetic poles,

168

Lodestones, 106, 159
Lost volts, 305

Luminous vapor lamps, 525, 526, 527
Machines, electrical, 46, 47, 48, 49, 50

classes of, 550
Magnet, origin of name, 105

the earth a, 116

tractive power of, 406

turning moment of, 149
Magnets, aging of, 167

artificial, 109

fables of ancients relating to, 107

laminated, 166

lifting power of, 124

most suitable metal for making, 160

mutual action of, 115

natural, 105

principle of manufacture, 161

strength of, 125
Magnet cores, 561
Magnet, electro, 403
Magnetic attraction, 112

explained, 120

mutual, 114

takes place through intervening

bodies, 113

Magnetic blowout, 485
Magnetic circuit, law of, 400
Magnetic declination, 169
Magnetic dip, 171
Magnetic elements, 175

variation of, 176 .
Magnetic field about wire carrying a
current, 346, 347, 348

coil rotating in, 551



Magnetic field, defined, 134

determination of strength of, 148,
149, 150

direction of, 135

effect on cathode rays, 673

effect on positive column, 669

force exerted upon conductor car-
rying a current, 356

graphic representation of intensity
of, 145

intensity of, 136

Magnetic fields, comparison of, 146,
147

compounding, 141
Magnetic figures, 138, 139, 140, 141

use of, 140
Magnetic flux, 142
Magnetic force, 115, 123
Magnetic forces, measurement of, 127
Magnetic inclination, 171
Magnetic intensity, 174
Magnetic lines of force, 137, 143

methods of mapping, 138, 139, 141

pass preferably through magnetic
substances, 143

properties of, 142, 143
Magnetic maps, 170
Magnetic meridian, 168
Magnetic moment, 130
Magnetic needle, polarity of, 116
Magnetic pole defined, 126

unit, 133
Magnetic poles, 110

inseparable, 111
Magnetic saturation, 393
Magnetic screen, 113, 143
Magnetic shell, 369
Magnetic storms, 180
Magnetic substances, 121
Magnetic variation, 169
Magnetism, 151

earth's, theories of, 181

Ewing's theory of, 153, 395

free, 142

intrinsic, 142

molecular, 152, 395

Tesidual, 155, 398, 562
Magnetite arc lamp, 523



INDEX.



589



Magnetization accompanied by molec-
ular movement, 154
by divided touch, 163
by double touch, 163
by electric current, 164
by induction, 118, 570
by single touch, 162
characteristic, 584
confined to outer layers of magnet,

166

curves of, 394
cycle of, 398
effect of heat on, 158
facilitated by molecular movement,

155

facilitated by solution, 159
facilitated by vibration, 156
loss facilitated by vibration, 157
Magneto-motive force, 400
Make and break, induced E. M. F.

at, 437

Manganin, 289

Manufacture of aluminum, 489
of calcium carbide, 488
of carborundum, 488
of electric lamps, 506
of magnets, 162, 163, 164

principle of, 161
Mapping magnetic lines of force, 138,

139, 141

Maps, magnetic, 170
Marconi, 698, 699, 703
Mariner's compass, 182

adjustment of, 183
Mariotte's law, 256

osmotic pressure follows, 264
Mass, unit of, 8

of corpuscles, 684
Maximum current from multiple

grouping, 340

Maximum flux, law of, 144
Maximum output of power by motor,

597
Maxwell's displacement assumption,

690
electro-magnetic theory of light, 548,

690, 694
law, 144, 371, 377, 467, 470, 471, 591



Maxwell's theory, confirmation by

Hertz, 694, 695-

Mean spherical candle power, 509
Measure of self induction, 433
Measurement, absolute, of current,

374

of resistance, 542, 546
Measurement of current by tangent

galvanometer, 374, 546
of E. M. F. by voltmeter, 461
of E. M. F. of cells, 329, 461
of electric power, 497, 498, 635
of high resistance, 326
of internal resistance of cells, 328
of magnetic forces, 127
of osmotic pressure, 261
of power by electro-dynamometer,

498

of resistance, 308
by drop of potential, 309, 310
by Wheatstone bridge, 317, 318,

319, 320, 321

of resistance of electrolytes, 327
with potentiometer, 332
Measurements, electrical effects used

in, 444, 445, 446,
electro-chemical effect standard for,

448
electro-chemical effect unsuited for

commercial needs, 451
electro-magnetic effect used in, 452,

453

electro-static, 98
Mechanical potential, 71
Mechanical production of electrical

current, 423
Medium, variation of electric force

with intervening, 55, 58
Mercury arc rectifier, 654, 655
Mercury vapor lamp, 527
Meridian, magnetic, 168
Mesh grouping, 646
Metal, most suitable for making

magnets, 160
Meter bridge, 325
Method by oscillations, 129, 131
of weakening controlling force of
galvanometers, 366



590



INDEX.



Methods of self-excitation, 563, 638
Metric system, 6
Microhm, 288
Mil foot, 296
Millivoltmeter, 473

as ammeter, 474
Millivoltmeter shunt, 475
Mirror galvanometer, 377
Moissan's furnace, 487
Molecular magnetism, 152, 395
Molecular movement facilitates mag-
netization, 155

magnetization accompanied by, 154
Molybdenite as detector for wireless,

705

Moment, magnetic, 130
Moore light, 526
Morse, 411
Morse alphabet, 412

telegraph, 412
Motor, 550

direction of rotation of, 604

efficiency of, 596

explanation of motion, 591

identical with generator, 590

induction, 428, 662, 663, 664, 665

maximum output of power by, 597

power developed by, 592

power proportional to counter E.
M. F., 594

repulsion, 662

series, 602
for A. C., 659
speed of, 603

shunt, 599 _

control of speed of, 600

synchronous, 660

operation of, 661
Motors, alternating current, 657

classes of, 658

classes of D. C., 598
Motor generator, 605, 648, 653
Moving iron instruments, 464
Multiple grouping of cells, 339
Multiplier, 469

Schweigger's, 365
Multipolar alternator, 639
Multipolar generator, 561, 578



Multipolar generators, advantages of,

574, 639

Natural magnets, 105
Nature of corpuscles, 685
Needle, dipping, 172

magnetic polarity of, 116
Negative electricity, 674
Negative glow, 670
Negative ions, 672
Nernst, 278
Nernst lamp, 508, 512
Neutral plane, 551, 570
Neutral temperature, 529
No field release, 601
No voltage release, 601
Norman, Robert, 171
Objections to lead batteries, 249
Observations of Pfeffer, 262, 263
Oerstedt's discovery, 344, 363
Ohm, the, 284, 543, 546

defined in terms of column of mer-
cury, 291, 543

international, 291, 543
Ohm's law, 297, 299, 307, 538
Open and closed coils, 559
Operation of synchronous motors, 661

of telephone, 442

of transformer, 650
Oscillations, method by, 129, 131
Oscillator, 694

Oscillatory discharge of Ley den jar,
686, 689

Feddersen's proof of, 688

Thomson's proof of, 687
Osmosis, 259
Osmotic pressure, 259

demonstration of, 260

follows Mariotte's law, 264

measurement of, 261

variation of, 263, 264, 265, 266
Ostwald, 272
Overcompounding, 589
Overload switch, 306, 414
Parallel grouping of cells, 336, 337

diagrams, 342
Parallel-series grouping, 339

diagrams, 342
Paramagnetics, 122



INDEX.



591



Peltier effect, 530
Pendulum, electric, 22
Period, 608
Permeability, 391, 397

expression for, 392
Pfeffer, observations of, 262, 263
Phase, 609
Phase difference, 609
Photometry, 510
Pierce, 699, 705
Pile, voltaic, 190
Pitch blende, 679
Plane development of drum winding,

576

Plante cell, 240

Plates, storage battery, dimensions of,
242

grouping of, 243

preparation of, 239
Platinum thermometer, 290
Points, effect of, 42, 43

experiments with, 43, 44
Polarity of electro-magnet, rule for,

404

Polarization, 198
Pole, magnetic defined, 126

rotation by current, 350

unit, 133, 535
Poles, consequent, 165

earth's, location of, 168
misnamed, 117

magnetic, 110

inseparable, 111
Polonium, 679

Polyphase alternators, 640, 644, 645
Positive column, 668

effect of magnetic field upon, 669
Positive rays, 676
Potential at point due to a charge, 74

difference, 73

drop of, 298, 299

electric, 70, 72, 73, 74, 75, 83
analogues of, 70
how measured, 72

mechanical, 71

zero, 73
Potentiometer, arrangement of, 330

calibration of, 331



Potentiometer, forms of, 333

measurement with, 332
Power, apparent, 635
defined, 492

developed by motor, 592
development in a battery, 495
electric, absolute unit of, 496
commercial unit of, 496
expression for, 494
measurement of, 497, 498, 635
practical unit of, 496
transmission of, 501, 502, 656
from primary cells, cost of, 343
in A. C. circuit, 634
maximum output by motor, 597
measurement of, by electro-dyna-
mometer, 498
of motor proportional to counter

E. M. F., 594
tractive, of magnet, 406
Power E. M. F., 617
Power factor, 635
Practical unit of capacity, 95
of current, 228, 307, 448, 546
of E. M. F., 427
of electric power, 496
of quantity, 228
of resistance, 284, 546
of self induction, 433, 434
Preparation of plates of storage bat-
tery, 239
Pressure, variation of resistance with,

285

gaseous, laws of variation, 256
osmotic, 259
demonstration of, 260
follows Mariotte's law, 264
measurement of, 261
variation of, 263, 264, 265, 266
Primary cell, 201, 202

cost of power from, 343
Primary electro-magnetic units, 538
Prime conductor, 47
Primer, electric, 483
Principle of electrometers, 100
of induction motor, 663
of tangent galvanometer, 375
of wireless telegraphy, 698



592



INDEX.



Production of current by rotating coil,
553

of rotating field, 664
Proof plane, 38
Quadrant electrometer, 103

theory of, 104

Quantity, electro-static unit of, 56,
535

units of, 536
Radio-activity, 679
Haftometer, 533
Radio-micrometer, 534
Radium, 679
Rays, alpha, 679

Becquerel, 679, 680

beta, 679

canal, 676

cathode, 671, 672, 680

effect of electric field on, 674
effect of magnetic field on, 673

gamma, 679

Lenard, 677, 680

positive, 676

Rontgen, 678

X, 678, 679, 680, 684
Reactance, capacity, 628

inductive, 619

Reaction, armature, 570, 587
Reactions of chloride accumulator,
244

of Edison battery, 251
Reactive E. M. F., 619
Receiving circuit for wireless, 704

tuning of, 706

Recording wattmeter, 499, 500
Rectification of A. C., 556, 653

of single phase current, 655
Rectifier, crystal, 705

electro-chemical, 653

mercury arc, 654, 655
Reflecting galvanometer, 378
Relay, 412, 703, 704, 705

sensitiveness of, 705
Reluctance, 391, 400

specific, 400
Reluctivity, 400
Remedy for local action, 197
Repulsion, electric, 22, 30



Repulsion motor, 662

Requirements of arc lamp mechanism,

517

of voltaic cell, 200
Residual charge, 87
Residual magnetism, 155, 398, 562
Resistance, 292

absolute measurement of, 542
absolute unit of, 427, 546



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