An alternator is a device that converts mechanical energy into electrical energy, primarily used in vehicles. It generates alternating current (AC) electricity, which is then converted to direct current (DC) to charge the battery and power the electrical systems when the engine is running. Typically driven by the engine's crankshaft, the alternator consists of a rotor and a stator. As the rotor spins, it creates a magnetic field that induces an electric current in the stator windings. This process is essential for maintaining the battery's charge and ensuring that components like headlights and the radio function properly while driving.