An electric current, often strong, brief, and luminous, in which electrons jump across a gap. Electric arcs across specially designed electrodes can produce very high heats and bright light, and are used for such purposes as welding and illumination in spotlights. Unwanted arcs in electrical circuits can cause fires. Lightning is a case of an electric arc between one cloud and the earth or another cloud, as are sparks caused by discharges of static electricity.
continuous, high-density electric current between two separated conductors in a gas or vapour with a relatively low potential difference, or voltage, across the conductors. The high-intensity light and heat of arcs are utilized in welding, in carbon-arc lamps and arc furnaces that operate at ordinary air pressure, and in low-pressure sodium-arc and mercury-arc lamps.
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