Electrical resistivity and conductivity results in the important concept of "quasineutrality", which says the density of negative charges is approximately equal to the density of positive charges over large volumes of the plasma ("n" = <Z>"n"), but on the scale of the Debye length there can be charge imbalance. In the special case that "double layers" are formed, the charge separation can extend some tens of Debye lengths. The magnitude of the potentials and electric fields must be determined by means other than simply finding the net charge density. A common example is to assume that the electrons satisfy the Boltzmann relation: Differentiating this
Positive real numbers of the logarithmic scale. For purposes of international standards ISO 80000-3 the dimensionless quantities are referred to as levels. Positive real numbers In mathematics, the set of positive real numbers, formula_1, is the subset of those real numbers that are greater than zero. The non-negative real numbers, formula_2, also include zero. The symbols formula_3 and formula_4 are ambiguously used for either of these, so it safer to always specify which. In a complex plane, formula_5 is identified with the positive real axis and is usually drawn as a horizontal ray. This ray is used as reference in the polar form