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 thought of as resulting from the subtraction of a larger number from a smaller. For example, negative three is the result of subtracting three from zero: In general, the subtraction of a larger number from a smaller yields a negative result, with the magnitude of the result being the difference between the two numbers. For example, since . The relationship between negative numbers, positive numbers, and zero is often expressed in the form of a number line: Numbers appearing farther to the right on this line are greater, while numbers appearing farther to the left are less. Thus zero appears