Which type of power flows back and forth in an AC circuit without doing any useful work?

In an AC circuit, reactive power is the type of power that flows back and forth without doing any useful work. It is associated with the energy alternately stored in electric and magnetic fields, which occurs in components like inductors and capacitors. Unlike active power, which performs actual work in a circuit such as lighting a bulb or powering a motor, reactive power oscillates in the circuit and does not contribute to the net energy consumed over time.

Reactive power is critical for maintaining the voltage levels necessary for active power to be effectively utilized, and its presence supports the functioning of inductive loads. Understanding reactive power is essential in power system design and analysis, especially for ensuring that systems run efficiently while maintaining a power factor that minimizes losses.