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
Negative number A solution can be to parenthesize the unary "−" along with its operand. For example, the expression may be clearer if written (even though they mean exactly the same thing formally). The subtraction expression is a different expression that doesn't represent the same operations, but it evaluates to the same result. Sometimes in elementary schools a number may be prefixed by a superscript minus sign or plus sign to explicitly distinguish negative and positive numbers as in Addition of two negative numbers is very similar to addition of two positive numbers. For example, The idea is that two debts can