Question

Calculate the total heat dissipated in a resistor of 50 Ω when 1.4 A current flows through it.

(a) 98 W

(b) 92 W

(c) 91 W

(d) 93 W

I got this question in class test.

Origin of the question is Speed Control of Shunt or Separately Excited Motors in division Speed Control of Direct Current Motors & Induction Motors of Electric Drives

Answer 1

The correct choice is (a) 98 W

Explanation: 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=1.4×1.4×50=98 W.