An inductor (or reactor or coil) is a passive two-terminal electrical component used to store energy in a magnetic field. Any conductor has inductance although the conductor is typically wound in loops to reinforce the magnetic field.
Due to the time-varying magnetic field inside the coil, a voltage is induced, according to Faraday's law of electromagnetic induction, which by Lenz's law opposes the change in current that created it. Inductors are one of the basic components used in electronics where current and voltage change with time, due to the ability of inductors to delay and reshape alternating currents. Inductors called chokes are used as parts of filters in power supplies or can be used to block AC signals from passing through a circuit.