Question

The expression of current obtained from the circuit in terms of differentiation from the circuit shown below?

(a) di/dt+i=4

(b) di/dt+2i=0

(c) di/dt+2i=4

(d) di/dt-2i=4

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

My doubt is from DC Response of an R-L Circuit in division Transients of Network Theory

Answer 1

The correct answer is (c) di/dt+2i=4

To explain: Let the i be the current flowing through the circuit. By applying Kirchhoff’s voltage law, we get 15 di/dt+30i=60 => di/dt+2i=4.