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 element to the natural order on the real numbers, but only to some extent. For example, it respects multiplication by positive reals and addition of self-adjoint elements, but formula_76 need not hold for positive elements formula_77 with formula_78 and formula_79. Positive element In mathematics, especially functional analysis, a self-adjoint (or Hermitian) element formula_1 of a C*-algebra formula_2 is called positive if its spectrum formula_3 consists of non-negative real numbers. Moreover, an element formula_1 of a C*-algebra formula_2 is positive if and only if there is some formula_6 in formula_2 such that formula_8. A positive element is self-adjoint and thus normal. If