At a point 20cm  from the centre of a uniformly charged dielectric sphere of radius 10cm , the electric field is 100V/m  . The electric field at 3cm   from the centre of the sphere will be

Electric field outside of the sphere  Eout=kQr2     .......iElectric field inside the dielectric sphere  Ein=kQxR3     .......iiFrom (i) and (ii),  Ein=Eout×r2xR3 ⇒At 3 cm,  E=100×3202103=120  V/m.