# Dictionary

## electron volt

Standard unit of energy in particle physics. One electron volt is the energy gained by an electron that is being accelerated by an electric potential difference (“electric voltage”) of 1 volt. One electron volt, in short: 1 eV is equivalent to 1.602176·10-19Joule (the Joule being the energy unit of the SI system of units).

Multiples of eV that are commonly used are

kilo-electronvolt: 1 keV = 1000 eV

Mega-electronvolt: 1 MeV = 1,000,000 eV =10^{6} eV

Giga-electronvolt: 1 GeV = 1,000,000,000 eV =10^{9} eV

Tera-electronvolt: 1 TeV = 1,000,000,000,000 eV =10^{12} eV.

Making use of the equivalence between mass and energy, eV/c² is commonly used as a unit for particle masses, with c the speed of light. As it is usual in particle physics to use a system of units in which light speed is equal to one, *c=1*, mass values are often simply given in eV, without explicitly mentioning the factor c².

The energy that is necessary to remove an electron from an atom is typically in the range of between a few and a few dozen eV. Typical energies of x-ray photons are in the keV range. The mass of an electron is 511 keV, that of a proton 938 MeV. Each proton in the proton beams of the Large Hadron Collider, the particle accelerator at the CERN laboratory, is accelerated to an energy of about 7 TeV.

As the temperature is a measure of the average energy with which each component participates in a system’s disordered thermal motion, it can be measured in eV as well, where 1 eV corresponds to 11,604 Kelvin.