Generator

A generator (also called an alternator or dynamo) is a device that converts kinetic energy into electrical energy using electromagnetic induction.

How an AC generator works

1. A coil of wire rotates between the poles of a permanent magnet (or a magnet rotates inside a fixed coil).
2. As the coil cuts through the magnetic field lines, an electromotive force (EMF) is induced across the coil (Faraday’s law).
3. The direction of the induced EMF reverses every half-turn of the coil, producing alternating current (AC).
4. Slip rings and carbon brushes maintain a continuous electrical connection between the rotating coil and the external circuit.

Output

The voltage output follows a sinusoidal wave pattern. It reaches a peak when the coil is horizontal (cutting field lines at the maximum rate) and drops to zero when the coil is vertical (momentarily moving parallel to the field lines).

Increasing the output

The induced EMF can be increased by:

• Rotating the coil faster (increases the rate of cutting field lines)
• Using a stronger magnet
• Increasing the number of turns on the coil
• Placing a soft iron core inside the coil

AC generator vs DC generator

An AC generator uses slip rings (continuous rings). A DC generator uses a split-ring commutator, which reverses the connections every half-turn so the output current always flows in the same direction. The output of a DC generator is a pulsating DC (not smooth).