INDFA". 



Heating of dynamos, 148 

 Heat, radiant, definition of, 308 



run, the, 149 

 Hefner, the, 311 



the spherical-, 311 



lamp, the, 310 

 Homopolar dynamo, the, 71 

 Hysteretic coefficients, table of, 380 

 Hysteresis loss in iron, 380 



magnetic, 379 



Illumination, the problem of, 321 



intensity of, 312 

 Impressed electromotive force, definition 



of, 97 



Incandescent lamp, see glow lamp. 

 Induced electromotive force, 30 

 Inductors, armature, 420 

 Insulation of dynamos, 167 

 of pole lines, 304 

 strength of, 299 

 of underground, station, and house 



wires, 305 

 Internal characteristic of series generator, 



386 



of shunt generator, 398 

 Iron and steel wire, weights and re- 

 sistances of, 307 



Joule's law, 20 



Kelvin's law of economy, 295 

 limitations of, 299 



Lamination of dynamo iron, 49 

 Lamp, the arc, 327 



efficiency, 326 



the electric, 325 



the Hefner, 310 



globes, shades and diffusers, 338 



the mercury-vapor, 350 



metal-filament glow, 348 



the Nernst, 349 



the osmium, 348 



ihe tantalum, 348 

 Lamps, dim versus bright, 323 



standard, 310 



Lap windings, 423 

 Lead, angle of, 94 



of brushes, 91 



backward, 94 



forward, 94 



Leakage, magnetic, 371 

 Lenz's law, 30 



Life of carbon-filament glow lamps, 344 

 Light, amount of required for illumina- 

 tion, 324 



conical intensity of, 311 



definition, 308 



distribution of, around a lamp, 314 



flux measurement of, 316 



luminous intensity of, 309 



physical intensity of, 308 



sectional intensity of, 311 

 Lighting, electric, 308 



of streets, 325 



Lightning and lightning arresters, 21 1 

 Linear expansion, coefficients of, 283 

 Lines, mechanical stresses in, 276 

 Load-factor of a station, definition of, 226 

 Local action and voltaic action, 240 

 Loss, armature, in generators and motors, 

 129 



field, in generators and motors, 127 



stray power, in generators and 



motors, 129, 130 



Losses in generators and motors, 127 

 Lumen, definition of the, 312 

 Lux, the, definition of, 311 



Magnetic circuit, the, 366 



field, direction of, 5 

 due to a wire, 13 

 in a long solenoid, 19 

 homogeneous and non-homoge- 

 neous, 5 

 intensity of, 4 



figures, 7 



flux, definition of, 8 

 in iron, 359 



hysteresis, 379 



leakage, 371 



coefficient of a dynamo, 372 



p?' meability, 365 



