Regardless of how many charged bodies there may be an a place of interest, and regardless of their shape or size, the potential at any point can be calculated from Poisson's or Laplace's equations.
Sometimes you may see versions of these equations with factors such as 4π or c scattered liberally throughout them. If you do, my best advice is to white them out with a bottle of erasing f...Sometimes you may see versions of these equations with factors such as 4π or c scattered liberally throughout them. If you do, my best advice is to white them out with a bottle of erasing fluid, or otherwise ignore them. They serve no scientific purpose, and are merely conversion factors between the many different systems of units that have been used in the past. The equivalent of Poisson's equation for the magnetic vector potential on a static magnetic field:
