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One electronvolt is a very small amount of energy:
: 1 eV = 2002 recommended values)

The unit electronvolt is accepted (but not encouraged) for use with SI . It is widely used in Solid State , Atomic , Nuclear , and Particle Physics , often with SI Prefix es m, k, M, or G.


USING ELECTRONVOLTS TO MEASURE MASS

Einstein reasoned that energy is equivalent to (rest) Mass , as famously expressed in the formula '' E=mc&2 '' (1 kg = 90 petajoules). It is thus common in Particle Physics , where mass and energy are often interchanged, to use eV/''c''² or even simply eV as a unit of mass. (The latter is only strictly valid when working in Natural Units where '' C ''=1.)

For example, an electron and a Positron , each with a mass of 0.511 MeV/c², can annihilate to yield 1.022 MeV of energy. The Proton (which is a member of the Baryon family of particles) has a mass of 0.938 GeV, making GeV a very convenient unit of mass for Particle Physics .
:1 eV/c² = 1.783 kg
:1 keV/c² = 1.783 kg
:1 MeV/c² = 1.783 Kg
:1 GeV/c² = 1.783 Kg

In some older documents, one sometime encounters the symbol "BeV", which stands for "billion-electron-volt"; it is equivalent to the GeV (gigaelectronvolt).


ELECTRONVOLTS AND KINETIC ENERGY

For comparison:

  • 3.2 Joule or 200 MeV - total energy released in Nuclear Fission of one U-235 atom (on average, it depends on the precise break up)

  • 3.5 joule or 210 MeV - total energy released in fission of one Pu-239 atom (on average, it depends on the precise break up)

  • Molecular Bond Energies are on the order of an electronvolt per molecule.

  • The typical atmospheric molecule has an energy of about 0.03 EV . This corresponds to Room Temperature .



ELECTRONVOLTS AND TEMPERATURE

In certain fields, such as Plasma Physics , it is convenient to use the electronvolt as an unit of temperature. The conversion is defined using ''k'', the Boltzmann Constant .

:{1 \mbox{ eV} \over k} = {1.6022 imes 10^{-19} \mbox{J} \over 1.380650 imes 10^{-23} \mbox{J/K}} = 11605 \mbox{ K}

For example, a typical Magnetic Confinement Fusion plasma is 15 keV, or 174 megakelvins.


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