In the circuit shown in the figure values of the circuit elements are , , , , and . We have to find the values of and (a) immediately after switch S is closed; (b) a long time later; (c) immediately after switch S is opened again; (d) a long time later.

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(a)

Immediately after the switch S is closed, there will be no flow of current in the inductor. At that instant current will flow through resistances and and its magnitude will be

(b)

A long time after the switch S has been closed, the flow of current through the inductor will stabilise and there will be no change in current flow. The values of currents and can be obtained by applying Kirchoff’s laws to loops. We have two linear equations for determining and .

Substituting the values of , , and , and solving the linear equations, we find

(c)

Immediately after the switch S is opened, the current will be zero and the current will be equal to the steady state current flowing through the inductor; and will be

(d)

A long time later both currents and will be zero.