A starter motor is an electric motor that is used to start an internal combustion engine. It is typically powered by a battery, and draws a high amount of current for a short period of time. An alternator is a device that converts mechanical energy into electrical energy. It is typically driven by the engine, and produces alternating current (AC). The AC is then converted to direct current (DC) by a rectifier, which can then be used to charge the battery or power other electrical devices in the vehicle.
While an alternator is not necessary for a starter motor to function, it is an important part of the vehicle's electrical system. Without an alternator, the battery would eventually become discharged, and the vehicle would no longer be able to start.
