For charging those a continuous current from the main is most convenient, some simple arrangement to regulate the rate of charge being all the intervention necessary. Such arrangement acts by way of resistance, allowing only the proper amount of current to pass from the main along the accumulator circuit.

Incandescent lamps suitably combined in parallel are com- monly used for this purpose, their capacity being known and their action easily observed. Thus, at 100 volts one 16 candle- power lamp takes J ampere—in other words, lets £ ampere pass on to [charge the accumulator. One 32 candle-power lamp will take 1 ampere, as also will two 16 candle-power lamps in parallel; so that, by arranging the power and number of lamps placed in parallel, an accumulator may be charged at any desired rate.

Fig. 19 shews diagrammatically an arrangement with four lamps in parallel, the positive terminal of the accumulator being connected direct to the positive pole of the supply, while the negative terminal has an ammeter and the lampresistance interposed in its connection with the negative pole of the main.

Any wire of a pair connecting a lamp with the main circuit may be tapped for charging an accumulator by cutting it at some point, and connecting the severed ends to the proper respective terminals. But a more convenient method is to make or obtain some permanent arrangement of lamps, as shewn in Fig. 20. This may be connected with the main by a plug when required, and from its terminals connections passed to the accumulator. With lamps in circuit, the correctness of the connecting, as regards polarity, may be judged from the brightness of their incandescence. When connection is correct, the lamp or lamps will burn dimly, since the residual current of the cells will be opposed to that of the main. If the connections be reversed, the lamp will burn very brightly, since the accumulator current will then reinforce that of the main.

But the method by use of litmus-paper, previously de- scribed, may prove more definite. Once determined, the polarity of the arrangement employed should be marked for future guidance.

No related posts.