Question

The value of the time constant in the R-L circuit is?

(a) L/R

(b) R/L

(c) R

(d) L

This question was posed to me by my school teacher while I was bunking the class.

Origin of the question is DC Response of an R-L Circuit in section Transients of Network Theory

Answer 1

Right option is (a) L/R

Easy explanation: The time constant of a function (V/R)e^-(R/L)t is the time at which the exponent of e is unity where e is the base of the natural logarithms. The term L/R is called the time constant and is denoted by ‘τ’.