Two conducting spheres of radii r1 and r2 are charged such that they have the same electric field on their surfaces. The ratio of the electric potential at their centres is :
Electric field on the surface of conducting sphere=kQR2
according to given condition
kq1r21=kq2r22
⟹q1q2=r21r22 −(1)
ratio of potentials at centre
=kq1r1kq2r2=q1q2⋅r2r1
substituting q1q2from (1)
we get
ratio=r1r2 Ans.