Everything about Electric Arc totally explained
An
electric arc is an
electrical breakdown of a gas which produces an ongoing
plasma discharge, resulting from a current flowing through normally
nonconductive media such as
air. A synonym is
arc discharge. The phenomenon was first described by
Vasily V. Petrov, 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
emergent properties of nonlinear patterns of
current and
electric field. The arc occurs in the gas-filled space between two conductive
electrodes (often made of
carbon) and it results in a very high
temperature, capable of
melting or
vaporizing most materials. An electric arc is a continuous discharge, while a similar electric
spark discharge is momentary. An electric arc may occur either in direct-current circuits or in alternating current circuits. In the latter case, the arc may re-strike on each half cycle of the current. An electric arc differs from a
glow discharge in that the current density is quite high, and the voltage drop within the arc is low; at the
cathode the current density may be as high as one million amps per square centimeter.
Uses
Industrially, electric arcs are used for
welding,
plasma cutting, for
electrical discharge machining, as an
arc lamp in
movie theater projectors, and
Followspots in
stage lighting.
Electric arc furnaces are used to produce
steel and other substances.
Calcium carbide is made in this way as it requires a large amount of energy to promote an
endothermic reaction (at temperatures of 2500
°C).
Low-pressure electric arcs are used for lighting, for example,
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:
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's 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.
Further Information
Get more info on 'Electric Arc'.
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