Question

The expression of current in R-L circuit is?

(a) i=(V/R)(1+exp⁡((R/L)t))

(b) i=-(V/R)(1-exp⁡((R/L)t))

(c) i=-(V/R)(1+exp⁡((R/L)t))

(d) i=(V/R)(1-exp⁡((R/L)t))

I had been asked this question during an internship interview.

The query is from DC Response of an R-L Circuit in portion Transients of Network Theory

Answer 1

Correct choice is (d) i=(V/R)(1-exp⁡((R/L)t))

Easiest explanation: The expression of current in R-L circuit is i = (V/R)-(V/R)exp⁡((R/L)t). On solving we get i = (V/R)(1-exp⁡((R/L)t)).