Whenever an electric current flows through a conductor, a magnetic field is immediately brought into existence in the space surrounding the conductor. It can be said that when electrons are in motion, they produce a magnetic field. The converse is also true i.e. when a magnetic field embracing a conductor moves relative to the conductor, it produce  a flow of electrons in the conductor. This phenomenon whereby an e.m.f.  and hence current  is induced in any conductor which is cut across or is cut by a magnetic flux is known as electromagnetic induction