The action of moving in a curved or bow-shaped path; also, the formation of an electric arc or spark between two conductors.
From Old English 'arc' (curved line or bow), present participle form; in electrical contexts, the term emerged in the 19th century to describe the visible electric discharge phenomenon.
Lightning is basically giant arcing—electricity jumping the gap between clouds and ground—and that's the same principle behind how old electric lights and modern arc welding work.
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