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 very serious ethical questions need come into play before stealing could justify killing. Positive obligations confer duty. But as we see with the police officer, exercising a duty may violate negative obligations (e.g. not to overreact and kill). For this reason, in ethics positive obligations are almost never considered "prima facie". The greatest negative obligation may have just one exception—one higher obligation of self-defense—but even the greatest positive obligations generally require more complex ethical analysis. For example, one could easily justify failing to help, not just one, but a great many injured children quite ethically in the case of triage