For a RL circuit, write a diffedrential equation in which the only time dependant quantity is current (use Kirchoff's loop). Derive an expression for current, i(t), in terms of L,R, and Vo. If Vo=5V, R=2.5 ohms, L=100 nH, what is energy stored at switch closed t=0, t=1 nano second, t=1 micro second?