In order to analyze and interpret a.c. data obtained from dielectric measurements of insulator materials, attemps have been made to understand the a.c. behaviour of simple R.C. circuits, so than an appropriate simulation can be made. The plots and some data from insulator materials are presented including the well known temperature and frequency dependance of the resistive component. The analysis of simple R.C. circuits is intended to help the understanding of the complex behaviour of insulators.