37. There are three methods in general use by which electric incandescent lamps are connected in circuit, namely, the multiple-arc, or parallel, system, the multiple-series system, and the three-wire system.

Multiple-Arc System

Fig. 26 shows the multiple-arc system, where the negative conductor a b and the positive conductor c f supply current to the lamps from the constant-potential dynamo d. The lamps l, l, etc. are connected in parallel between the two conductors, and the amount of current to be furnished depends directly upon the number of lamps used. Each lamp is entirely independent of all the others, and its extinction does not affect the brightness of the rest.

Multiple Arc System 475

Fig. 26.

The lamps used in this system should all be of the same working voltage, and equal to that maintained between the two conductors. If the E. M. F. between these is 110 volts, only 110-volt lamps must be used.