Electric arc
Electricity arcs between the power rail and electrical pickup "shoe" on a
London Underground train
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".
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 virtually anything.
A
compact disc safely etched by a microwave oven to create an electrical plasma arc held within the plastic media itself.
Capturing the various shapes of the plasma path of an electrical arc has been demonstrated in a
G4techTV technology tips video to destroy data on
compact discs by placing the compact disc (up to about 4 or so) into a standard
microwave oven on high for about 10-15 seconds. Each resulting disc art is unique—no two discs are ever the same. As with any electrical arc application,
common sense care should be observed in this process. The plastic compact disc media will get instantly hot in this process so waiting a few seconds after the etching process is required not to burn yourself. This applies in the same way to most microwaved food applications in general. The only undesired side effect of this process is a slight displeasing odor. It should be noted that recordable CDs use organic dyes. These organic compounds are liable to change once exposed to high-heat arcing so the displeasing odor may be toxic.
On a commercial basis, electric arcs are used for
welding,
plasma cutting, for
electrical discharge machining, as an
arc lamp in
movie theater projectors or
street lamps (historic), and to produce
aluminum and sometimes
steel using
scrap.
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, e.g., fluorescent tubes, mercury and sodium street lamps, camera flash lamps, plasma displays, and neon signs.
See also
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