The mechanical paddles in a pinball machine are actuated by "solenoids", essentially electromagnets. These devices act like inductors as far as the circuits that must drive them are concerned. To activate a paddle, a current is applied via a mechanical switch to the solenoid, which drives the paddle; to return the paddle to its resting position, the current is removed (switch released). Since the solenoid appears inductive, it will resist this change in current, developing a potentially destructive voltage. The voltage can cause arcing between the switch contacts, leading to failure. To prevent this, a device is placed across the solenoid (inductor) that can hold the voltage to a safe value, say 40V, during transients. If the activating current in the solenoid is 1 amp and its inductance is 100uH, how long after the switch is turned off does it take for the current in the inductor to ramp down to zero? Where does the energy that was stored in the inductor go?