How is alternating current produced in generators?

Alternating current (AC) in generators is produced by rotating a coil in a magnetic field, causing the current to change direction.

In more detail, the process of generating alternating current involves a device known as an AC generator or alternator. This device works based on the principle of electromagnetic induction, discovered by Michael Faraday. The alternator consists of a rotating magnet (rotor) and a stationary coil of wire (stator). The rotor is turned by an external force, such as a wind turbine or a steam turbine.

As the rotor spins, it creates a changing magnetic field that passes through the stator. This changing magnetic field induces a voltage in the stator coil. The direction of the induced current changes with the change in direction of the magnetic field. This is due to Faraday's law of electromagnetic induction, which states that the induced electromotive force (or voltage) in a closed circuit is proportional to the rate of change of magnetic flux through the circuit.

When the rotor is at 0° or 180°, the magnetic field lines are parallel to the coil and the rate of change of magnetic flux is zero, hence no current is induced. However, when the rotor is at 90° or 270°, the magnetic field lines are cutting through the coil at the maximum rate, inducing the maximum current. As the rotor continues to rotate, the direction of the magnetic field changes, causing the direction of the induced current to change as well. This results in an alternating current, which changes direction periodically.

The frequency of the alternating current depends on the speed of rotation of the rotor. The faster the rotor spins, the higher the frequency of the alternating current. This is why in power stations, the speed of the turbines is carefully controlled to maintain a constant frequency.