The circuit of Problem 7.31 has a 50-V source of opposite polarity switched in at t = 0.50 ms, replacing the first source. Obtain the current for

(a) 0 < t < 0.50 ms,

(b) t > 0.50 ms.

Data from problem 7.31

A series RL circuit, with R = 100 Ω and L = 0.2 H, has a 100-V source applied at t = 0; then a second source, of magnitude 50 V with the same polarity, is switched in at t = t′, replacing the first source. Find t′ such that the current is constant at 0.5 A for t > t′.