Electric Conduction in Hard Rubber, Pyrex, Fused and Crystalline Quartz

The study of physical and electrical characteristics of insulating materials is of growing importance to the electrical industry because of the ever increasing potentials employed in electric generating and distributing equipment. The particular problem presented in this paper is related to engineering practise because polarization and conduction both result in the conversion of electric energy into heat. This produces increased local and general heating, which may be contributing causes to the progressive deterioration and final breakdown of the insulation. The constant potential method explained in this paper provides a means for studying the inherent voltage-current-time relations which are masked in experiments using alternating applied potential. Part of the material contained in this paper was presented by the writer to the faculty of the Graduate School of Cornell University for the degree of Doctor of Philosophy. The investigation was later continued with the joint support of the Hecksher Research Council and the General Electric Company. Several methods were tried for obtaining conducting surfaces on the specimens for constant potential tests. An improved method was devised for making tests and experimental results on four materials were obtained. Peculiar reversals were observed in the charge and discharge curves for fused quartz. The summary of experimental results is followed by suggestions for further research along similar lines.