An alternator converts mechanical energy to electrical energy in the form of alternating current using a rotating magnetic field and stationary armature. It has a rotor that acts as the rotating magnetic field and a stator that houses the armature windings. As the rotor rotates, the changing magnetic field induces current in the stator windings based on Faraday's law of electromagnetic induction. Alternators can have either a cylindrical or salient pole rotor design and are used in various applications depending on their size and rotation speed.