A generator rotor is a rotating electromagnetic device that is used to create electrical current. The rotor consists of a cylindrical core made of ferromagnetic material, such as iron, and winding wires that carry the current. The number of ohms that a generator rotor should have depends on the application for which it will be used. For example, a low-ohm rotor would be used in an electric motor, while a high-ohm rotor would be used in an alternator or generator.