Electric arc



     

An electric arc is an air. A synonym is arc discharge. The phenomenon was first described by Vasily V. Petrov (Василий В. Петров), a Russian scientist who discovered it in 1802. An archaic term is voltaic arc as used in the phrase "voltaic arc lamp".

Overview

The various shapes of electric arc are cathode the current density may be as high as one million amps per square centimeter. [1]

Uses

On a commercial basis, electric arcs are used for welding, °C).

Low-pressure electric arcs are used for lighting, e.g., fluorescent tubes, mercury and sodium street lamps, and camera flash lamps.

Electric arcs have been studied for electric propulsion of spacecraft.

Undesired arcing

Undesired or unintended electric arcing can have detrimental effects on electric power transmission and distribution systems and electronic equipment. Undesired arcing in electrical contactors can be suppressed by various devices, including:

  • immersion in inert gas or vacuum
  • arc chutes
  • magnetic blowouts

An electric arc has a non-linear relationship between current and voltage. Once the arc is established (either by progression from a glow discharge or by momentarily touching the electrodes then separating them), increased current results in a lower voltage between the arc terminals. This negative impedance effect requires that some positive form of impedance to be placed in the circuit, if it is desired to maintain a stable arc. This property is the reason uncontrolled electrical arcs in apparatus become so destructive, since once initiated an arc will draw more and more current from a fixed-voltage supply until the apparatus is destroyed.

See also

  • Arc transmitter
  • Arc welding
  • Arc lamp
  • Spark gap
  • Vacuum arc

References

  1. ^ A. H. Howatson, An Introduction to Gas Discharges, Pergamon Press, Oxford pgs. 80-95
 
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