Mutual Inductance

When an emf is produced in a coil because of the change in current in acoupled coil , the effect is called mutual inductance. The emf is described by Faraday's law and it's direction is always opposed the change in the magnetic field produced in it by the coupled coil (Lenz's law ). The induced emf in coil 1 is due to self inductance L. The induced emf in coil #2 caused by the change in current I1 can be expressed as

The mutual inductance M can be defined as the proportionalitiy between the emf generated in coil 2 to the change in current in coil 1 which produced it.

The most common application of mutual inductance is the transformer.