(a) Two spheres have radii a and b and their centers are a distance d apart. Show that the capacitance of this system is provided that d is large compared with a and b. (Suggestion:
Because the spheres are far apart, assume that the potential of each equals the sum of the potentials due to each sphere, and when calculating those potentials assume that V = keQ/r applies.)
(b) Show that as d approaches infinity the above result reduces to that of two spherical capacitors in series.