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## The electron-volt (unit of energy)

In particle physics, a unit of energy is commonly used: the electron-volt (eV).

1 eV = 1.6 10^{-19} Joules

- A 60 Watts electric lamp uses 60 Joules per second to give some light to you.
- 1 GeV = 1 billion of electron-volts
- A flying mosquito (0.01 g) is composed of about 3 10
^{19}
atoms and, to climb one meter, it needs about 0.0001 Joule,
that is about 30 millionth of electron-volt per atoms of mosquito.

Moreover, particles masses are expressed in a more convenient way thanks to the electron-volt.

The famous equation **E = mc**^{2} gives the following relationship:

1 eV/c^{2} = 1.8 10^{-36} kg

An electron, for instance, has a mass of 511 keV, that is about 10^{-30} kg.

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Last update: 26/06/1999 : http://wwwlapp.in2p3.fr/neutrinos/agev.html
Didier Verkindt