The alternator is related to its cousin the dynamo in that both convert mechanical energy into electricity. Unlike the dynamo, which creates direct current (DC), the alternator produces alternating current (AC) by rotating an armature through a magnetic field. It is essentially an electromagnet rotating within coils of wire.

The alternator makes use of the principal of electrical induction, discovered by Michael Faraday and Joseph Henry working independently in 1831. They found that moving an electrical conductor, such as a wire, across lines of magnetic force caused an electric current to flow in the wire. Alternatively, moving a magnet within a coil of wire induced electricity to flow through the wire. In addition, when the movement of the magnet was reversed, the electrical flow also reversed--alternating the movement of the magnet created an alternating current. Faraday showed that voltage could be produced by magnetism provided three conditions existed: there...