Electric arc

Electric arc, area of intense light and heat produced by the passage of electricity across a small gap between 2 electrodes. Electricity is able to span the gap because it ionizes the surrounding air, which then serves as a conductor. The arc light, which uses carbon electrodes, is commonly used as a spotlight in the theater and as a floodlight. The heat produced by an arc is used in welding to melt metal rods, which solidify to provide a strong joint between 2 metal surfaces.