. The principles of physics. core F is therefore drawn up into thebobbin, lifting the upper carbon andestablishing the arc. Should the car-bons become too widely separated,the resistance of the arc, and con-sequently of the coarse wire circuiton C, increases, diminishing the cur-rent in C and increasing that in the shunt S. The field dueto the shunt is therefore strengthened, and that due to thecoarse ^wire diminished, allowing the coreF to fall slightly, bringing the carbonsnearer together. By the device of thetwo opposing fields, due to the coils onC being wound in opposite directions,the fe
. The principles of physics. core F is therefore drawn up into thebobbin, lifting the upper carbon andestablishing the arc. Should the car-bons become too widely separated,the resistance of the arc, and con-sequently of the coarse wire circuiton C, increases, diminishing the cur-rent in C and increasing that in the shunt S. The field dueto the shunt is therefore strengthened, and that due to thecoarse ^wire diminished, allowing the coreF to fall slightly, bringing the carbonsnearer together. By the device of thetwo opposing fields, due to the coils onC being wound in opposite directions,the feeding of the lamp is done auto-matically, and the actual distance of thetwo carbons varies but little. 547. Incandescent electric lamps.—Theincandescent (or glow) light is pro-duced by the heating of some refractorybody to a state of incandescence by thepassage of an electric current. Carbonfilaments are now almost exclusivelyused in incandescent lamps. The fila-ment of the Edison lamp is carbonized bamboo. It is essential. INCANDESCENT ELECTRIC LAMPS. 591 that the oxygen of the air be removed from these bulbs, other-wise the carbons would be quickly burned out; hence veryhigh vacua are produced in the bulbs with a mercury pump. Fig. 479 represents an Edison lamp. The loop or filamentof carbon, L, is joined at n n to two platinum wires which passthrough the -closed end of the glass tube, T. One of these wiresis connected with the brass ring, B, and the other with thebrass button, D, at the bottom of the lamp. When the lampis screwed into its socket, connection is made with the linethrough pieces of brass in the socket which are insulatedfrom each other. An Edison 16 ( lamp has a resistance (whenhot) of about 140 ohms, the difEerence of potential at itsterminals is about110 volts, and itrequires a currentof lamp con-sumes about one-tenth of a horse-power. Incandescentlamps are usuallyintroduced into the circuit in multiple arc (Eig. 480), thecurre
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Keywords: ., bookcentury1800, bookdecade1890, booksubjectphysics, bookyear1895
