Electromagnetic induction is the production of an electrical potential difference (or voltage) across a conductor situated in a changing magnetic field. Michael Faraday was the first to describe this phenomenon mathematically: he found that the size of the voltage produced is proportional to the rate of change of the magnetic flux. This applies whether the flux itself changes in strength or the conductor is moved through it. Electromagnetic induction underlies the operation of generators, induction motors, and most other electrical machines[?].
Faraday's law of electromagnetic induction states that
Further, Lenz's law gives the direction of the induced emf, thus:
See Maxwell's equations for further mathematical treatment.