Which electrical component performs both an electrical and mechanical function?

The starter solenoid is the correct answer because it serves a dual function in the starting system of an engine. Electrically, the solenoid acts as a switch that controls the flow of current from the battery to the starter motor. When the ignition key is turned, a small electrical current energizes the solenoid, causing it to close the circuit and allow a larger current to flow to the starter motor, which is necessary to crank the engine.

Mechanically, once the solenoid is energized, it operates a lever or plunger that engages the starter gear with the engine flywheel. This mechanical action is crucial for initiating the engine's rotation. Thus, the starter solenoid effectively combines both electrical control and mechanical operation in one component, making it a unique and essential part of the vehicle's starting system.

In contrast, the battery charger primarily serves an electrical purpose by supplying power to charge the battery without any mechanical action. The voltage regulator ensures that the voltage delivered to electrical components remains stable, without performing any physical movement itself. A fuse primarily acts as a safety device to interrupt electrical flow in case of an overload, thus not having any mechanical function.