Self capacitance

If the capacitance can be represented by a matrix, then the question of what is meant by the diagonal terms of the capacitance matrix naturally arises. These are referred to as the self capacitances. Define the background potential at a surface to mean that part of the scalar potential which is due entirely to the charges on the other surfaces. Then the charge on a surface is equal to the self capacitance of that surface times the difference between its scalar potential and the background potential.