the amount that flows in each branch depends, as you will learn in the next lesson, on the amount of resistance in it.
We can carry our discussion of this circuit one step further, and anticipate what we are going to learn in the next lesson. The total resistance in the circuit is less than the value of the smallest resistance in parallel. Furthermore, the current in each branch is less than the total current since the sum of the currents in all the branches is equal to the total current. See if you can’t figure this out from the water analysis shown in Fig. 12.
Most practical electrical circuits are combinations of series and parallel, known as the series-parallel, or parallel-series circuits. In fact, the current shown in Fig. 8 is really a series-parallel
Fig. 12
circuit--the source of e.m.f. and rheostat are connected in series and the loads in parallel.
A series-parallel arrangement is usually used where it is desired to operate a number of similar electrical devices, such as lamps or motors, from a line, the voltage of which is several times that required to operate a single lamp or motor. For example, a series-parallel circuit is used in the light wiring of street cars. Here the source of supply is generally 550 volts, therefore five 110-volt lamps of similar current-carrying capacity are connected in series across the circuit and groups of five connected in parallel as shown in Fig. 13(a). From what you have learned about series circuits you know the great disadvantage of this arrangement--if any lamp in a series group burns out, the remaining lamps in that series group will not light. You will
