Mechanics of the household; a course of study devoted to domestic machinery and household mechanical appliances . henplaced on the Dim-a-lite, makes electrical con-tact as in an ordinary socket but with thedifference that in series with the lamp filamentis the rheostat, by means of which additional re-sistance may be added to change the current flow-ing in the lamp. The rheostat is so arranged that contact may bemade at four different points in the resistance coil, through whichthe electricity may be varied from 100 to 20 per cent, of thenormal quantity. The resistance in any case permits curr
Mechanics of the household; a course of study devoted to domestic machinery and household mechanical appliances . henplaced on the Dim-a-lite, makes electrical con-tact as in an ordinary socket but with thedifference that in series with the lamp filamentis the rheostat, by means of which additional re-sistance may be added to change the current flow-ing in the lamp. The rheostat is so arranged that contact may bemade at four different points in the resistance coil, through whichthe electricity may be varied from 100 to 20 per cent, of thenormal quantity. The resistance in any case permits current topass through the filament in amounts of 70, 30 and 20 per cent, ofthe normal amount. In use, the variation is made by pulling onestring to add resistance and thus dim the light; or by pulling theother string, the resistance is decreased and more electricitypasses through the filament to produce a brighter light. Thequantity of light given out by the filament does not vary in theratio of the added resistance but a variable light is obtained atthe expense of a small amount of electricity which is changed. Fig. 223.—The resistancetype of ** turn-down lamp. 324 MECHANICS OF THE HOUSEHOLD
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