An alternator is a device that converts mechanical energy into electrical energy. The alternator is powered by an external system which turns a rotor that creates an alternating magnetic field. This field is then transformed into electrical energy by the alternator's stator, which is a stationary component that contains coils of wire. The alternator works by using a series of diodes to convert the alternating current generated by the rotor into direct current. When choosing an alternator for your vehicle, it's important to consider several key factors, including output, size, mounting, and cost.