Page "Coefficients of potential" Paragraph 20

| r < sub > i </ sub >-r < sub > j </ sub >|, i. e. the distance from the area-element da < sub > j </ sub > to a particular point r < sub > i </ sub > on conductor i. σ < sub > j </ sub > is not, in general, uniformly distributed across the surface.

Let us introduce the factor f < sub > j </ sub > that describes how the actual charge density differs from the average and itself on a position on the surface of the j-th conductor: