4. Consider the circuit diagram below; assume the switch has been in the initial position for a long time,

and it switches position as indicated at t = 0.

a. Find i(t) through the inductor for all t > 0.

b. Sketch i(t) as current vs. time; annotate critical values on your sketch.

c. How much energy is stored in the inductor at t = ∞?

20 mA

ww

20 Ω

i(t)

t = 0

m

120 mH

ww

30 Ω

O

10 mA