In a purely inductive AC circuit, how does the current relate to the voltage?

In a purely inductive AC circuit, the relationship between current and voltage is characterized by the phenomenon of phase shift. Specifically, in this type of circuit, the current lags the voltage by 90 degrees.

This occurs because, in an inductor, the voltage leads the current due to the energy storage feature of inductors. When an alternating current flows through an inductor, the magnetic field builds up and induces a voltage that opposes the change in current. As a result, it takes time for the current to reach its maximum value after the voltage has already reached its peak. This time delay leads to the lag of current behind voltage, which corresponds to a phase difference of 90 degrees.

Understanding this phase relationship is essential in analyzing AC circuits, as it explains how inductive components behave compared to resistive components, where current and voltage are in phase, and capacitive components, where current leads voltage. In purely inductive circuits, recognizing the lagging current is crucial for calculating power factor, impedance, and designing efficient electrical systems.