A spherical capacitor is comprised of a solid inner conduction sphere of radius a with positive charge Q and an isolated, concentric, thin outer conduction shell of radius b and charge -Q. Derive the capacitance expression for this arrangement. What is the value of the capacitance for a = 10mm and b = 15 mm?
Then what is the capacitance if the outer shell is removed, i.e. for an isolated sphere?