Currents Through Parallel Resistances:
Refer to the schematic diagram which is as shown below. The total parallel resistance in the circuit is R, battery voltage is E, current in branch n, having resistance Rn, is measured by ammeter A and is termed In.
The sum of all the In values in the circuit is equivalent to the sum current I drawn from the source. This is the current is divided up in the parallel circuit, likewise to the way that voltage is divided up in a series circuit.
Figure: Analysis of current in a parallel dc circuit.
PROBLEM:
Assume that the battery in the figure below delivers 12 V. Further assume that there are 12 resistors, each of 120 ohms in the parallel circuit. Compute the total current I drawn from the battery?
SOLUTION:
At first, find the total resistance. This is simple since all the resistors have similar value. Divide Rn = 120 by 12 to obtain R = 10 ohms. Then the current I is found by using Ohm's law:
I = E/R = 12/10 = 1.2 A