<P> Carbon arc lights were the first electric lights . They were used for street lights in the 19th century and for specialized applications such as searchlights until World War 2 . Today, low - pressure electric arcs are used in many applications . For example, fluorescent tubes, mercury, sodium, and metal halide lamps are used for lighting; xenon arc lamps are used for movie projectors . </P> <P> Formation of an intense electric arc, similar to a small - scale arc flash, is the foundation of exploding - bridgewire detonators . </P> <P> A major remaining application is in high voltage switchgear for high - voltage transmission networks . Modern devices use sulphur hexafluoride at high pressure in a nozzle flow between separated electrodes within a pressure vessel . The AC fault current is interrupted at current zero by the highly electronegative SF6 ions absorbing free electrons from the decaying plasma . A similar air - based technology has largely been replaced because many noisy units in series were required to prevent the current re-igniting under similar supergrid conditions . </P> <P> Electric arcs have been studied for electric propulsion of spacecraft . </P>

A(n) is an extremely high-temperature discharge produced by an electrical fault in the air