Electromagnetic Induction
As said earlier; in 1820, Oersted discovered the magnetic effect of electric current ie. when a steady current flows through a conductor, a magnetic field is produced around it. In 1831, Michael Faraday discovered the effect, called electromagnetic induction, just converse to the magnetic effect of electric current.
When a coil made of copper wire is placed inside a magnetic field, magnetic flux is linked with the coil. Faraday found that when the magnetic flux linked the coil is changed", an electric current starts flowing in the coil, provided the coil with is a closed one. In case the coil is open, an e.m.f. is set up across the two ends of the coil respectively. The induced current and the e.m.f. in the coil last only so long coil as the magnetic flux linked with the coil keeps on changing.
Thus, electromagnetic induction is the phenomenon of production of electric current (or e.m.f.) in a coil, when the magnetic flux linked with the coil is changed.