In the circuit from Problem 1 below the inductor has a nonze

In the circuit from Problem 1 below, the inductor has a nonzero resistance. Find the maximum value of this resistance so that the current at t=400 mu sec is not reduced from the ideal value by more than 1%.

Solution

At t <0 the switch is closed and due to reverse bias the diode is at off stage. Then

R=E÷I

I=E÷R

at t>0 I_inf=0

tow=L÷R

I=(E/R)*exp (-Rt/L)