Arc

[technoguy]

An electric arc is an electrical breakdown of a gas which produces an ongoing plasma discharge, similar to the instant spark, resulting from a current flowing through normally nonconductive media such as air. A slightly archaic term is voltaic arc as used in the phrase "voltaic arc lamp".

[vipl]

A luminous discharge of current that is formed when a strong current jumps a gap in a circuit or between two electrodes. The arc produces a temperature of several thousand degrees, and the tips of the carbon rods are heated to incandescence, creating light. The rods are slowly vaporized during the process and need to be regularly adjusted to maintain the arc.