A spherical capacitor consists of two concentric spherical conductors, held in position by suitable insulating supports (Fig. 2.36). Show that the capacitance of a spherical capacitor is given by `C = (4piepsilon_0r_1r_2)/((r_1)-(r_2))` where `r_1` and `r_2` are the radii of outer and inner spheres, respectively.: