Electric arc. In electricity , an electric arc or “electric arc” refers to the electric discharge that is formed between two electrodes subjected to a potential difference and placed within a rarefied gaseous atmosphere, usually at low pressure, or in the open air.
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It was first discovered and demonstrated by the British chemist Humphry Davy in 1800. To initiate an arc, the ends of two electrodes , usually pencil-shaped, usually graphite , are briefly contacted and a strong current (about 10 amps ) through them. This current causes great heating at the point of contact, as the electrodes separate, a light discharge similar to a flame is formed between them .
The discharge is produced by electrons ranging from the negative to the positive electrode, but also, in part, by positive ions moving in the opposite direction. The collision of the ions generates intense heat at the electrodes, the positive electrode heating up more because the electrons hitting it have higher total energy.
In an arc open to normal pressure air the positive electrode reaches a temperature of 3,500 degrees Celsius . During the discharge time there is a very intense luminosity and a great release of heat . Both phenomena should be accidental, can be extremely destructive, as with drilling isolators in transmission lines of electrical energy at high voltage or insulation of conductors and other electrical or electronic elements.
The arc power used in a controlled manner has been used as a source of light , before the invention of incandescent lamp and even after, in the film industry for strong light intensity in film making and in the projectors of rooms movie theater. The calorific effects of electric arc continue to be used in industry for metal welding and other metallurgical procedures.. In the latter type of applications, the intense heat generated by the electric arc is usually used in special furnaces to melt refractory materials. In this type of furnaces temperatures of the order of 3,500 ° C can be easily reached. This also allows products with a very high melting point to be melted. The particular advantage of this procedure is a complete independence when choosing the products to be applied ( scrap , sponge iron , pig iron and any mixtures). Modern kilns can have a capacity of up to 300 tons of steel and it takes about an hour and a half for each casting.