alternator corresponds to the combination of an electric coil and a
magnet which can rotate.
(At large scale, as in a power plants, the magnet is replaced by an
When the magnet rotates, magnetic poles approach and then move away
from the coil causing the appearance of a voltage: the electric coil
then acts an electrical generator.
When the magnet from an alternator (or electromagnet) rotates it has a
kinetic energy which is converted into electrical energy.
An alternator therefore convert a kinetic energy into electric energy