What is the function of the rotor brush?

The rotor brush plays a crucial role in delivering current to the spark plugs in an ignition system. Located within the distributor, the rotor spins to make contact with various terminals that are connected to the spark plugs through wires. As the rotor turns, it completes the electrical circuit necessary to transfer voltage from the ignition coil to each spark plug at the correct timing. This is essential for igniting the fuel-air mixture within the engine's cylinders, ensuring proper combustion and engine performance.

The other options involve different functions: one refers to charging the battery, which is typically the job of the alternator; another pertains to grounding the electrical system, a task usually handled by ground connections throughout the vehicle; and the last option is related to fuel delivery systems, which manage the flow of fuel rather than electrical functions. Thus, option A is the only choice that accurately describes the primary function of the rotor brush within the context of an ignition system.