Usually,
inductors have appreciable resistance in their windings, but we shall
assume that this inductor has negligible resistance Thus, the circuit is a purely inductive ac circuit Let
the voltage across the source be v = vm sinw t Using
the Kirchhoff’s loop rule, 
∑ε ( )t =
0 , and  since there
is no resistor in the circuit,
d
0
d
i
v
L
t
−
=
(7