An electronvolt (symbol: eV) is the amount of energy gained by a single unbound electron when it falls through an electrostatic potential difference of one volt. This is a very small amount of energy:

1 eV ≈ 1.602 × 10-19 J.

In particle physics, the megaelectronvolt (1 MeV = 106 eV) is also used to measure masses of elementary particles, using the conversion from special relativity
E = m c2
where E stands for energy, m for mass and c for the speed of light in vacuum. In these units, the mass of an electron is about 0.5 MeV, and that of a proton is about 940 MeV.

For comparison, charged particles in a nuclear explosion range from 0.3 to 3 MeV. The typical atmospheric molecule has an energy of about 0.03 eV.

To convert a particle's energy in electronvolts into its temperature in kelvin, divide by 11,604. See also: Orders of magnitude

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