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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

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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