Usually inductor doesn't allow the sudden increase in current .Because the inductor will produce magnetic field when current passes through it.This magnetic field produces some emf due to self inductance princple.the induced back emf opposes the normal current flow.after sometimes the circuit gets stabilised ....The time taken for stabilization is known as transient time....therefore in this circuit if voltage is suddenly increased ....the current also gets increased proportionally...as the inductor doesn't allow sudden current hikes...it will resist the current for few milliseconds ..At that time the current will flow into the other branch and makes the bulb glow for the transient time...
The inductor discharge can be seen by opening the switch.
Note:: if the resistor connected series is removed....the circuit will gets shorted after the transient time ..so it won't work.
