Arc discharge

Article By:

Alexeff, Igor Department of Electrical and Computer Engineering, University of Tennessee, Knoxville, Tennessee.

Lonngren, Karl E. Department of Electrical and Computer Engineering, University of Iowa, Iowa City, Iowa.

Last reviewed:October 2019

DOI:https://doi.org/10.1036/1097-8542.046800

A type of electrical conduction in gases characterized by high current density and low potential drop. The electric arc was discovered by Humphry Davy in 1808, when he connected a piece of carbon to each side of an electric battery, touched the two pieces of carbon together, then drew them slightly apart. The result is a dazzling steam of ionized air, or plasma, at a temperature of 6000°C (10,800°F), the surface temperature of the sun. A typical arc runs at a voltage drop of 100 V with a current drain of 10 A. The arc has negative resistance-the voltage drop decreases as the current increase-so a stabilizing resistor or inductor in series is required to maintain it. The high-temperature gas rises like a hot-air balloon while it remains anchored to the current-feeding electrodes at its ends. It thereby acquires an upward-curving shape, which accounts for its being called an arc.

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