Common Core Ground School 2 Practice Exam

The main idea here is energy transformation: turning mechanical energy from rotating motion into electrical energy. That conversion is what a generator does. It uses electromagnetic induction—when the rotor spins inside a magnetic field, electrical current is generated in the windings and can be supplied to circuits. The other items have different roles: a battery stores chemical energy and outputs electrical energy without converting mechanical energy, while a generator control unit and an emergency power unit manage or provide power rather than perform the energy conversion. So the device that converts mechanical energy to electrical energy is the generator.