Dipole Moment Fluctuations of a Dielectric Body

Abstract

Frohlich's theory of dielectrics has shown that a dielectric body will exhibit spontaneous fluctuations in dipole moment as a result of thermal agitation. It is pointed out that these fluctuations may arise from a variety of sources and that each source is intimately connected with a particular mechanism of polarization. The particular case of a dielectric which has two mechanisms of polarization (orientational and displacement) is considered. Frohlich's relations for the total mean square fluctuation in dipole moment of a dielectric sphere are modified so as to yield an expression for the fluctuations arising from only one polarization mechanism (the orientational). It is shown that Frohlich's free energy method of computing these fluctuations is independent of the dynamic properties of the dielectric. The recent work of Harris and Alder is shown to be in error.