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Encyclopedia > Electric arc
A 3000 volt electricity arc between two nails
Electricity arcs between the power rail and electrical pickup "shoe" on a London Underground train
An electric arc can melt calcium oxide

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. [1] A termite cathedral mound produced by a termite colony: a classic example of emergence in nature. ... In electricity, current refers to electric current, which is the flow of electric charge. ... In physics, the space surrounding an electric charge or in the presence of a time-varying magnetic field has a property called an electric field. ... Alternative meanings: There is also an Electric-type Pokémon named Electrode. ... For other uses, see Carbon (disambiguation). ... For other uses, see Temperature (disambiguation). ... In physics, melting is the process of heating a solid substance to a point (called the melting point) where it turns into a liquid. ... â€œVaporizationâ€ redirects here. ... Look up Spark in Wiktionary, the free dictionary. ... Electric glow discharge is a type of plasma formed by passing a current at 100V to several kV through a gas - usually argon or another noble gas. ... Diagram of a copper cathode in a Daniells cell. ...

On a commercial basis, 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). Welding is a fabrication process that joins materials, usually metals or thermoplastics, by causing coalescence. ... Plasma cutting is a process that is used to cut steel and other metals (or sometimes other materials) using a plasma torch. ... Electrical Discharge Machine Electrical discharge machining (or EDM) is a machining method primarily used for hard metals or those that would be impossible to machine with traditional techniques. ... 15 kW Xenon short-arc lamp. ... 35 mm Kinoton movie projector in operation. ... Followspot is a generic term used to describe any number of lighting instruments used to highlight performers on stage. ... This is a current Stagecraft collaboration! Please help improve it to good article standard. ... An electric arc furnace is a system that heats charged material by means of an electric arc. ... For other uses, see Steel (disambiguation). ... Calcium carbide is a chemical compound with the chemical formula CaC2. ... In thermodynamics, the word endothermic describes a process or reaction that absorbs energy in the form of heat. ... For other uses, see Chemical reaction (disambiguation). ... Celsius is, or relates to, the Celsius temperature scale (previously known as the centigrade scale). ...

Low-pressure electric arcs are used for lighting, e.g., fluorescent tubes, mercury and sodium street lamps, and camera flash lamps. Fluorescent lamps in Shinbashi, Tokyo, Japan Assorted types of fluorescent lamps. ... A high pressure sodium vapor street lamp from Australia. ...

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. In electrical engineering, Impedance is a measure of opposition to a sinusoidal electric current. ...

// The arc converter, sometimes called the Poulsen arc, or arc transmitter, as it was commonly called, is a device used to convert DC energy into RF energy. ... Manual Metal Arc welding, also known as stick or MMA welding is one of the most common forms of welding. ... 15 kW Xenon short-arc lamp. ... A spark plug. ... A vacuum arc arises when the surface of metal electrodes in contact with a good vacuum begin to emit electrons because of heating or through exceeding the metals Work function. ...

## References

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

Results from FactBites:

 Arc-Welding Fundamentals | Lincoln Electric (887 words) In arc welding, the intense heat needed to melt metal is produced by an electric arc. An arc is created across the gap when the energized circuit and the electrode tip touches the workpiece and is withdrawn, yet still with in close contact. In welding, the arc not only provides the heat needed to melt the electrode and the base metal, but under certain conditions must also supply the means to transport the molten metal from the tip of the electrode to the work.
 Steel making with electric arc furnace (329 words) After samples have been taken to check the chemical composition of the steel, the electric arc furnace is tilted to allow the slag, which is floating on the surface of the molten steel, to be poured off. The electric arc furnace is then tilted in the other direction and the molten steel poured into a ladle, where it either undergoes secondary steelmaking or is transported to the caster. Every tonne of electric arc furnace steel uses about 7.4 GJ of energy compared with about 16.2 GJ for every tonne of BOS steel (7.4 GJ is still equal to the power consumption of a town of 100,000 population).
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