Breakdown of Glass with Alternating Potentials

Previous tests on the breakdown of glass with direct potentials indicated the existence of three different regions of breakdown. The present paper describes similar tests on alternating potentials. The following conclusions are reached: 1. Three distinct regions of breakdown are obtained on alternating current as well as on direct current. 2. In the disruptive and intermediate regions, breakdown occurs at an alternating peak voltage approximately equal to the direct breakdown voltage. 3. In the thermal region, breakdown occurs at an alternating peak voltage somewhat lower than the direct breakdown voltage.