Dynamo-Electric Machinery - A Manual for Students of Electrotechnics #252368

We may take it, therefore, that a system of 20 arcs in series will require a dynamo giving a current of, say, 10 amperes, and a pressure, when all the lamps are in use, of nearly 1000 volts. This allows 45 volts per lamp, and 5 volts more for driving the current through the resistance of the wires between each lamp and the next. Constant-current dynamos are also needed for the purposes of municipal lighting by means of special glow lamps (with thick carbon wires instead of thin filaments), connected in series, so that the same unvarying current flows successively through a large number of them.