Question

Find voltage across 12H inductor.

(a) 2V

(b) 10V

(c) 12V

(d) 20V

I had been asked this question in a national level competition.

This intriguing question originated from Coils Connected in Series in portion Inductance in a DC Circuit of Basic Electrical Engineering

Answer 1

The correct option is (c) 12V

To elaborate: e=Ldi/dt

Leq=2+10+12+20=44H

di/dt=44/44 = 1 A/s.

Voltage across 12H inductor = 12*di/dt = 12*1=12V.