The erosion of electrical contacts by the normal Arc

The cathode material transfer under the action of the `normal arc¿ has been measured for a number of elements and alloys. In all cases auxiliary circuits were used to record the accumulative arc duration and the voltage/current characteristics of the arc, from which the total arc energy as well as the total charge passed in the arc could be accurately calculated. Within the experimental errors the material transfer from the cathode was found to be directly proportional to the total charge passed in the arc¿a relationship first proposed by R. Holm. It is shown that, for most practical purposes, the cathode `normal arc¿ transfer can be calculated with a reasonable accuracy according to the formula given by Llewellyn Jones.