A uniform but time varying magnetic field B(t) exists in a circular region of radius a and is directed into the plane of the paper as shown in Fig. 25.21.
The magnitude of the induced electric field at point P at a distance r from the centre of the circular region
decreases as 1r
A time varying magnetic field produces an electric field. The magnitude of the electric field at a distance r from the centre of a circular region of radius a where a time varying field B exists is given by
E=a22rd Bd t
At r=a, E=(a2)dBdt, which the value of E at the edge of the circular region. For r > a, E decreases as 1r.