Considering the symmetry, we find that the potential is function of r only. The Laplace’s equation can be written as:

............(2.139)

From the above equation, by direct integration we can write,
...............................(2.140)
Applying boundary conditions

................................(2.141)
we can find C₁ and C₂ and the expression for the potential can be written as :  ...........................(2.142)

The electric field and the capacitor can be obtained using the same procedure described in Example -3.