Why is the alternator's voltage higher than the battery's?

The voltage output of the alternator is designed to be higher than that of the battery primarily to ensure that the battery can be fully charged and to effectively power the electrical systems of the vehicle. When the engine runs, the alternator generates electrical energy, and if its voltage output is greater than the battery's, it creates a potential difference that drives current into the battery.

This higher voltage is essential because it overcomes the internal resistance of the battery and ensures that the battery receives sufficient charge. Additionally, the alternator must supply power to various systems, such as lights, radio, and ignition, while also keeping the battery charged. The slightly elevated voltage helps achieve this dual purpose - charging the battery fully and providing necessary power to the vehicle's electrical components simultaneously.

The other options might have certain relevance, but they do not accurately capture the main reason for the alternator's higher voltage in relation to its function in the vehicle's electrical system.