Find the capacitance of a spherical capacitor whose electrodes have radii R1 and R2 > R1 and which is filled with isotropic dielectric whose permittivity varies as ε = a/r, where a is a constant, and r is the distance from the centre of the capacitor.
Let, us mentally impart a charge q to the conductor. Now potential difference between the plates,
Hence, the sought capacitance,
