Question

A complete 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? A. 10 A B. 13.32 A C. 8 A D. 3.33 A

Answer 1

The answer is D. 3.33 A

In parallel connected devices, circuits are also placed parallel. It is known that in parallel circuits, total voltage is equal to the voltage of each device. 

So, we know that:
Device 1 - R1 = 12 ohms
Device 2 - R2 = 4 ohms
Total voltage - V = 40V = V1 = V2

If V = I × R, for the first device is V1 = I1/R1.
⇒ I1 = V1 ÷ R1
⇒ I1 = 40 V ÷ 12 ohms
⇒ I1 = 3,33 A