College Physics 10th Edition by Raymond Serway,Chris Vuille

Exercise 30

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 a / k e = 4 0 a.