Plasma (physics) potential in the space between charged particles, independent of how it can be measured, is called the "plasma potential", or the "space potential". If an electrode is inserted into a plasma, its potential will generally lie considerably below the plasma potential due to what is termed a Debye sheath. The good electrical conductivity of plasmas makes their electric fields very small. This 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 (formula_6), but on the scale of the Debye length
Positive element Positive element In mathematics, especially functional analysis, a self-adjoint (or Hermitian) element formula_1 of a C*-algebra formula_2 is called positive if its spectrum formula_3 consists of non-negative real numbers. Moreover, an element formula_1 of a C*-algebra formula_2 is positive if and only if there is some formula_6 in formula_2 such that formula_8. A positive element is self-adjoint and thus normal. If formula_9 is a bounded linear operator on a complex Hilbert space formula_10, then this notion coincides with the condition that formula_11 is non-negative for every vector formula_12 in formula_10. Note that formula_11 is real for every formula_12 in formula_10