What happens to current in an inductive circuit when the switch is suddenly opened?

In an inductive circuit, when the switch is suddenly opened, the current does not drop to zero instantly due to the nature of inductance. Inductors resist changes in current flow. When the switch is opened, the inductor attempts to maintain the current that was flowing through it just before the switch was opened. This is because an inductor stores energy in its magnetic field, which is directly related to the current flowing through it.

As the circuit is suddenly interrupted, the current will not cease immediately; instead, it will gradually decay over time. This gradual decay occurs as the inductor releases the stored energy back into the circuit, which can take the form of a brief current surge or "back EMF", depending on the specifics of the circuit layout. The decay of current continues until all the energy stored in the magnetic field is dissipated, which can be observed as a decay curve on a graph of current over time.

This characteristic of inductors is critical in understanding how they operate in various applications, including power supplies and transformers, where maintaining current flow during interruptions can be crucial for correct functioning.