Difference between revisions of "Electronvolt"
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| − | The '''electronvolt''' (symbol: '''eV''') is a [[non-SI unit]] of [[energy]]. It is defined as the [[kinetic energy]] gained by an [[electron]] on | + | The '''electronvolt''' (symbol: '''eV''') is a [[non-SI unit]] of [[energy]] that has been accepted for use with the [[SI]] by the [[CIPM]].<ref name="SI">{{SIbrochure8th|pages=125–26}}.</ref> It is defined as the [[kinetic energy]] gained by an [[electron]] on passing through a [[potential difference]] of one [[volt]] in [[vacuum]]:<ref name="SI"/> as such, its value in [[SI unit]]s is determined by the measured value of the [[elementary charge]]. The 2006 [[CODATA]] recommended value is 1 eV = {{nowrap|1.602 176 487(40){{e|−19}} J}}.<ref name="CODATA-e">{{CODATA 2006|url=http://physics.nist.gov/cgi-bin/cuu/Value?e}}.</ref> |
In chemistry, it is often useful to express the electronvolt as a [[molar quantity]], whose value in SI units is determined by the measured value of the [[Faraday constant]]. The 2006 CODATA recommended value is 1 eV = {{nowrap|96.485 3399(24) kJ mol<sup>−1</sup>}}. | In chemistry, it is often useful to express the electronvolt as a [[molar quantity]], whose value in SI units is determined by the measured value of the [[Faraday constant]]. The 2006 CODATA recommended value is 1 eV = {{nowrap|96.485 3399(24) kJ mol<sup>−1</sup>}}. | ||
| − | In particle physics, | + | In particle physics, multiples of the electronvolt are also used as a units of [[mass]] based on the principle of [[mass–energy equivalence]]. The [[dimensional analysis|dimensionally correct]] unit of mass for use with the SI would be eV/''c''<sup>2</sup>, although the division by the square of the [[speed of light]] is often assumed and masses quoted simply in megaelectronvolts (MeV). |
==References== | ==References== | ||
Revision as of 10:11, 15 March 2010
The electronvolt (symbol: eV) is a non-SI unit of energy that has been accepted for use with the SI by the CIPM.[1] It is defined as the kinetic energy gained by an electron on passing through a potential difference of one volt in vacuum:[1] as such, its value in SI units is determined by the measured value of the elementary charge. The 2006 CODATA recommended value is 1 eV = 1.602 176 487(40) × 10−19 J.[2]
In chemistry, it is often useful to express the electronvolt as a molar quantity, whose value in SI units is determined by the measured value of the Faraday constant. The 2006 CODATA recommended value is 1 eV = 96.485 3399(24) kJ mol−1.
In particle physics, multiples of the electronvolt are also used as a units of mass based on the principle of mass–energy equivalence. The dimensionally correct unit of mass for use with the SI would be eV/c2, although the division by the square of the speed of light is often assumed and masses quoted simply in megaelectronvolts (MeV).
References
- ↑ 1.0 1.1 The International System of Units (SI), 8th ed.; International Bureau of Weights and Measures: Sèvres, France, 2006; pp 125–26. ISBN 92-822-2213-6, <http://www.bipm.org/utils/common/pdf/si_brochure_8_en.pdf>.
- ↑ Mohr, Peter J.; Taylor, Barry N.; Newell, David B. CODATA Recommended Values of the Fundamental Physical Constants: 2006. Rev. Mod. Phys. 2008, 80 (2), 633–730. doi:10.1103/RevModPhys.80.633, <http://physics.nist.gov/cuu/Constants/codata.pdf>. Direct link to value.
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