When current flows through a conductor, a magnetic field is formed around the conductor. When the conductor flows through alternating current, that is, the value and direction of current change periodically, the magnetic field also changes with it.

If a piece of metal or other conductor is placed in the alternating magnetic field, there will be electromotive force in it. Under the action of electromotive force, alternating current will be generated in the conductor. When an electric current flows in a metal block, it heats the metal.

The above heating method of putting metal into alternating magnetic field is called induction heating, and the conductor initially passing through alternating current is called inductive conductor or inductor.