Erg Abu Muharrik
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The erg is a unit of energy equal to 10−7 joules (100 nJ). It originated in the Centimetre–gram–second system of units (CGS). It has the symbol ''erg''. The erg is not an SI unit. Its name is derived from (), a Greek word meaning 'work' or 'task'. An erg is the amount of work done by a force of one dyne exerted for a distance of one centimetre. In the CGS base units, it is equal to one gram centimetre-squared per
second The second (symbol: s) is the unit of time in the International System of Units (SI), historically defined as of a day – this factor derived from the division of the day first into 24 hours, then to 60 minutes and finally to 60 seconds ...
-squared (g⋅cm2/s2). It is thus equal to 10−7 joules or 100 nanojoules (nanojoule, nJ) in SI units. * 1 erg = = * 1 erg = = = * 1 erg = = * 1 erg = = * 1 erg =


History

In 1864, Rudolf Clausius proposed the Greek word () for the unit of energy, work and heat. In 1873, a committee of the British Association for the Advancement of Science, including British physicists James Clerk Maxwell and William Thomson, 1st Baron Kelvin, William Thomson recommended the general adoption of the centimetre, the gramme, and the second as fundamental units (Centimetre–gram–second system of units, C.G.S. System of Units). To distinguish derived units, they recommended using the prefix "C.G.S. unit of ..." and requested that the word ''erg'' or ''ergon'' be strictly limited to refer to the ''C.G.S. unit of energy''. In 1922, chemist William Draper Harkins proposed the name micri-erg as a convenient unit to measure the surface energy of molecules in surface chemistry. It would equate to 10−14 erg, the equivalent to 10−21 joule. The erg has not been a valid unit since 1 January 1978 when the European Economic Community ratified a directive of 1971 that implemented the International System of Units, International System (SI) as agreed by the General Conference on Weights and Measures, General Conference of Weights and Measures. It is still widely used in astrophysics and sometimes in mechanics.


See also

* Foe (unit), relative measure for energy released by a supernova * Lumen second, for the lumerg and lumberg units * Metre–tonne–second system of units


References

{{CGS units Units of energy Centimetre–gram–second system of units