Inductors:

An inductor is a circuit element which will store electrical energy in the form of a magnetic field. It is commonly a coil of wire wrapped around a core of permeable material. A magnetic field is generated whenever current is flowing by the wire. If two circuits are arranged as in Figure, a magnetic field is produced around Wire A, but there is no EMF (electromotive force) induced into Wire B since there is no associative motion among the magnetic field and Wire B.

the current stops flowing in Wire A If we now open the switch, and the magnetic field collapses. As the field collapses, it moves associative to Wire B. Whenever this occurs, an EMF is induced in Wire B.

Figure: Induced EMF

This is an instance of Faraday's Law that begins in which a voltage is induced in a conductor whenever that conductor is moved by a magnetic field, or whenever the magnetic field moves past the conductor.  While  the  EMF  is  induced  within  Wire  B,  the  current  will  flow  whose  magnetic  field opposes the modify in the magnetic field which produced it.

For this purpose, an induced EMF is sometimes known as counter EMF or CEMF. This is an instance of Lenz's Law that states which the induced EMF opposes the EMF which caused it.