Question

A conducting sphere of radius a has charge q on it

Answer 1

A conducting sphere of radius a has a charge Q on it. It is enclosed by a neutral conducting concentric spherical shell having inner radius 2a and outer radius 3a. find electrostatic energy of system

ans.

First write the Electric field due to each sphere.

E1 = E3 =0 {inside the inner conductor from 0 to a and from 2a to 3a in conducting shell)

E2 and E4 = kQ/r^2

Now,

dU =0.5e{ E2^r^2dr(a to 2a) + E4^2r^2dr (3a to inifinity)}

put E2 and E4 and thhen integearte.