A spherical capacitor consists of a spherical conducting shell of radius b and charge Q concentric with

Question:

A spherical capacitor consists of a spherical conducting shell of radius b and charge –Q concentric with a smaller conducting sphere of radius a and charge Q.
(a) Find the capacitance of this device.
(b) Show that as the radius b of the outer sphere approaches infinity, the capacitance approaches the value α/ke = 4 πε0α.