It is known to you that ''whenever the flux of a magnetic field through the area bound by a closed conducting loop changes , an emf is produced in the loop . Then emf is given by epsi = -(dphi)/(dt) , where psi = int vecB dot "vecds is the flux of the magnetic flux through a closed loop changes, an electric current results. Let us now investigate " what is the external mechanism that maintains the electric field in the loop to drive the current". In the words what is the mechanism to produce an emf? (a) keeping ther magnetic field constant as time pases and moving whole as part of the loop. (b) Keeping the loop at rest and changing the magnetic field. (c) Combination of (a) and (b)that is by moving the loop ( partly or wholly) as well as by changing the field. The mechanism (a) for production of emf is studie under theheating motional emf and mechanism (b) under the heating induced electric field. In mechanism (a) , magnitude of the potential difference across the conductor is given by epsi=Blv where,B,l, v have their usual meanings and the electrostatic field developed within the conductor E=vB Whereas if the magnetic field through a stationary conduting loop is changing with time, then also there will be an induced emf whose value will be epsi=ointvecE.vecdl, where E is the induced electric field. The electric field produced by the changing magneticfield is non-electrostatic and non-conservation If the above magnetic field is present perpendicular to a ring of radius of 1 cm, mass=10 gram and charge =1 C, then the angular velocity of the ring as a function of time is ( the ring and the cylinderical region are coaxial)