Question

A wire is carrying a direct current of 20A and a sinusoidal alternating current of peak value 20A. Find the rms value of the resultant current.

(a) 24

(b) 24.5

(c) 25

(d) 25.5

The question was posed to me during an interview.

My doubt is from Voltage and Current Values of a Sine Wave in portion Introduction to Alternating Currents and Voltages of Network Theory

Answer 1

The correct answer is (b) 24.5

To elaborate: Direct current = 20A, sinusoidal alternating current of peak value = 20A. The rms value of the combined wave = √(20^2+20^2/2) = 24.5A.