The current in a 20 mH inductor is known to be i = 40 mA, t < 0; i = A,e~mm[ + yW-4()(X,0'A, 0. The voltage across the inductor (passive sign convention) is 28 V at t = 0.
a) Find the expression for the voltage across the inductor for t > 0.
b) Find the time, greater than zero, when the power at the terminals of the inductor is zero.