An alternating current (AC) generates a rotating magnetic field through the interaction of various magnetic fields.

When an alternating current flows through a coil, it produces a magnetic field that changes both direction and magnitude over time. This alternating magnetic field interacts with the magnetic field of a stationary magnet, resulting in a force that causes the coil to rotate. As the current continues to alternate, the magnetic field shifts direction, prompting the coil to rotate in the opposite direction.

In addition to single coils, a rotating magnetic field can be produced by employing multiple coils arranged in a specific configuration. This configuration is referred to as a polyphase system, where each coil is connected to different phases of the alternating current. The magnetic fields generated by each coil combine their effects to create a unified rotating magnetic field.

The speed of this rotating magnetic field is directly influenced by the frequency of the alternating current. Specifically, a higher frequency results in a faster rotation of the magnetic field. Consequently, the speed of electric motors can be effectively controlled by adjusting the frequency of the alternating current.