Low frequency dielectric behavior

Electrical engineers, as well as polymer physicists and materials researchers, can gain useful information from a study of the behavior of dielectrics, and of high-megohm resistors, at very low frequencies. This is illustrated by examples. There are two main methods of obtaining ultra-low-frequency data. One is to apply a d.c. voltage producing a time-dependent current which corresponds to an inverse frequency plot. The other is to use an alternating voltage, usually sinusoidal, and apply this to a bridge circuit including the material under study. Recent developments in the latter methods are presented, along with some typical results.