Suppose there is a steady current in an inductor. If you attempt to reduce the current to zero instantaneously by quickly opening a switch, an electrical arc can appear at the switch contacts. Why? Indeed, is it physically possible to stop the current instantaneously? Explain.

Question

Suppose there is a steady current in an inductor.  If you attempt to reduce the current to zero instantaneously by quickly opening a switch, an electrical arc can appear at the switch contacts.  Why?  Indeed, is it physically possible to stop the current instantaneously?  Explain.

anonymous · Answer

The inducer opposes the change in current i.e. since the current is decreasing, it tries to increase it (Lenz's law). It may sometimes even create 1000 Volts and this causes the spark to flow.

Current could be stopped instantaneously by connecting a suitable capacitor to the circuit. The capacitor will store the excess charge induced.