Question

Calculate the active power in a 1 Ω resistor with 2 A current flowing through it.

(a) 2 W

(b) 4 W

(c) 7 W

(d) 1 W

I have been asked this question during an interview.

My doubt stems from Effect of Starting on Power Supply, Motor and Load in chapter Starting of Electric Drives

Answer 1

The correct answer is (b) 4 W

To explain: The resistor is a linear element. It only absorbs real power and dissipates it in the form of heat. The voltage and current are in the same phase in case of the resistor so the angle between V & I is 90°. P = I^2R = 2×2×1=4 W.