.........................................(2.64)

Using the vector identity, ,where f is a scalar quantity , we have,

.......................(2.65)

Converting the first volume integral of the above expression to surface integral, we can write

.................(2.66)

where is the outward normal from the surface element ds' of the dielectric. From the above expression we find that the electric potential of a polarized dielectric may be found from the contribution of volume and surface charge distributions having densities

......................................................................(2.67)