In the context of magnetic storage and inductance, induction is magnetic or electromagnetic induction. Such magnetic induction occurs when the magnetic flux in a conductor or coil changes.
The induction creates an induction voltage, an electromotive force( EMF), in the conductor. This depends directly on the number of turns of the conductor, or inductance, on the change in the magnetic field line number, and on the time duration of the field line change. Induction requires a change of current, which is expressed by the relative change of the magnetic field to the conductor, or to the inductance, or by a change of the current in the conductor. With any induction, there is an opposing induction effect in the own inductance, the self-induction or counter-induction, which counteracts the increasing current flow and slows down the magnetic field build-up.
The physical principle of induction is used in the generation of electromagnetic waves, in loudspeakers, transformers, oscillating circuits, but also for the magnetization of particles on magnetic tapes, in nuclear memories, magneto-optical memories and other storage media that work with magnetizable layers such as floppy dis ks and hard disks.