Question

Find the time constant in a series R-L circuit when the resistance is 4 ohm and the inductance is 2 H.

(a) 0.25

(b) 0.2

(c) 2

(d) 0.5

This question was addressed to me in an interview.

The doubt is from Resistances and Capacitances topic in chapter Electrostatic Boundary Value Problem of Electromagnetic Theory

Answer 1

Correct answer is (d) 0.5

Explanation: The time constant for an R-L series circuit will be τ = L/R. Put R = 4 and L = 2. We get τ = 2/4 = 0.5 second.