Electromagnetic induction.

Electromagnetic induction is the phenomenon of production of an induced emf (electromotive force) in a closed circuit whenever the magnetic flux linked with the circuit changes.

The induced emf is given by

e=-dΦ/dt

For a coil of N-turns

e=-NdΦ/dt

where magnetic flux is

Φ=BAcosθ

Lenz's law:-

The induced current always flows in such a direction that it opposes the change in magnetic flux that produces it.