Networks Analysis and Synthesis - Engineering

Q1:

In given figure the switch was closed for a long time before opening at t = 0. The voltage Vx at t = 0+ is

A 25 V

B 50 V

C -50 V

D 0 V

ANS:C - -50 V

at t = 0, L will act as short circuit hence I = 2.5 A. Vx = 2.5 x 20  50v, but in opposite to current source. Hence Vx = - 50v.