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 and positive rights obligates others to act with respect to the right holder. In the framework of the Kantian categorical imperative, negative rights can be associated with perfect duties while positive rights can be connected to imperfect duties. Belief in a distinction between positive and negative rights is usually maintained, or emphasized, by libertarians, who believe that positive rights do not exist until they are created by contract. The United Nations Universal Declaration of Human Rights lists both positive and negative rights (but does not identify them as such). The constitutions of most liberal democracies guarantee negative rights, but not all include positive