A “coil” is a coil of wire that serves as an inductor. When current flows through a wire, a small magnetic field occurs around it, so a coil of such wire with a current flowing through it creates a stronger magnetic field than a smaller length of wire. The coil temporarily stores energy in the form of a magnetic field. The job of an inductor is to resist sudden changes in the current that flows through it. The current cannot instantly change; it always lags by a certain amount of time. Coils are used in electric motors, generators, electromagnets, transformers, and more. Coils are often used to control contactor switches to serve as magnetic motor starters. Coils have a limited lifespan, so replacement coils are good to keep on hand.