 For a given number "i" of edge channels each filled with "N" electrons per unit area, the overall number "n" of electrons per unit area will read

The overall number "n" of electrons per unit area is commonly referred to as the electron density of a sample.No electrons disappear from the sample into the unknown, so the electron density "n" is constant.It follows that

For a given sample, all factors including the electron density "n" on the right hand side of relationship () are constant.