Dielectric relaxation in liquids and solids

RELAXATION is the lag in the response of a system to change in the forces to which it is subjected.¹ It is thus a rather general phenomenon whose existence becomes apparent when its rate is not far from being of the same order of magnitude as that of the change of the applied forces. It may consist, for example, of lag in response to the following conditions: a change of temperature which affects the determination of thermal properties; a change of stress which affects mechanical stretching or viscous flow; or a change of electric field which tends to lower the dielectric constant. The relaxation rate is the rate at which a system comes into equilibrium with its surroundings when such a change occurs. When the relaxation rate is very different from that of the change of the constraining influence, the process involving the relaxation may not be noticed. For example, when a dielectric constant is measured at a frequency which is very low or very high in comparison with the dielectric relaxation rate, no loss of energy is observed.