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 with negative rights of physicians. In controversial areas such as abortion and assisted suicide, medical professionals may not wish to offer certain services for moral or philosophical reasons. If enough practitioners opt out as a result of conscience, a right granted by conscience clause statutes in many jurisdictions, patients may not have any means of having their own positive rights fulfilled. Such was the case of Janet Murdock, a Montana woman who could not find any physician to assist her suicide in 2009. This controversy over positive and negative rights in medicine has become a focal point in the ongoing