Consider two identical insulating spheres of radius R and uniform charge Q throughout their volume. They are separated from their centers by a distance of d>2R. My general equation for electrostatic potential energy is:
How would I determine an expression for the interaction energy between the spheres? Would I use the above equation and use rho from sphere 2 and phi from sphere 1, evaluated at 2?
How would this change if the charge were distributed across the surface instead of the volume?