Published online by Cambridge University Press: 15 February 2011
In general, a plasma consists of a mixture of electrons, ions,and neutral species. Although there are free electric charges in a plasma, negative and positive charges compensate each other, i.e. overall a plasma is electrically neutral, a property which is known as quasi-neutrality. In contrast to an ordinary gas, the free electric charges in a plasma give rise to high electrical conductivities which may even surpass those of metals. A hydrogen plasma, for example, at atmospheric pressure heated to temperatures of 106 K, has the same electrical conductivity as copper at room temperature. As the plasma temperature increases, the electrical conductivity increases beyond that of copper. Plasma temperatures of the order of 106 K and above are typical for thermonuclear fusion experiments.