For surface charge, .................................(2.32)

For volume charge, .................................(2.33)

It may be noted here that the primed coordinates represent the source coordinates and the unprimed coordinates represent field point.

Further, in our discussion so far we have used the reference or zero potential at infinity. If any other point is chosen as reference, we can write:

.................................(2.34)

where C is a constant. In the same manner when potential is computed from a known electric field we can write:

.................................(2.35)