Erosion of Electrical Contacts on Make

When an electric current is set up by bringing two contacts together, they necessarily discharge a capacity. If the discharge takes place through an arc before the metallic circuit is established, erosion of the electrodes results. In a low voltage circuit the occurrence of an arc is dependent upon the condition of the electrode surfaces and upon the circuit inductance. For ``inactive'' surfaces, and a voltage of the order of 50, an arc does not occur if the inductance is greater than about 3 microhenries. Surfaces of various metals can be ``activated'' by vapors of certain unsaturated organic compounds, and in the active condition they give arcs even when the circuit inductance is greater than this limiting value by a factor of more than 103. The study of arcs between active metal surfaces is not yet complete, and most of this paper and all of the remainder of this abstract have to do with surfaces which are inactive.When an arc occurs at the make of inactive metal surfaces, its energy, which in low volt...