Acomplete circuit contains two parallel-connected devices and a generator for providing the electromotive force. the resistance of the first device is 12 ohms, the resistance of the second device is 4 ohms, and the voltage developed by the generator is 40 v. what is the magnitude of the current flowing through the first device?

Parallel circuits are circuits when placed in a parallel position. Meaning that for each device, they have their own branch. The voltage that is received in the circuit is equal to the individual devices. The total current is equal to the current of each device. The resistance is the reciprocal of the resistances of each device combined.  

Given:
Device 1 = 12 ohms
Device 2 = 4 ohms
Voltage total = 40V  

Required:
Current at 12 ohms  

Solution:
40V = V1 =V2  

Since V =IR
I1 = V1/R1
I1 = (40V)/(12 ohms)
I1 = 3.334 A(Amperes)