Electronvolt
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 = 1.602176462 × 10-19 J.
Einstein taught us that energy is equivalent to
mass, as famously expressed in the formula
E =
m c².
Particle physicists thus use the eV/c² as unit of mass, with the advantage that conversion between mass and energy is then trivial.
For example, an electron and a positron, each with a mass of 511 keV/c² (this is not the actual mass of a proton), can annihilate to yield 1.022 MeV of energy.
- 1 eV/c² = 1.783 × 10-36 kg
- 1 keV/c² = 1.783 × 10-33 kg
- 1 MeV/c² = 1.783 × 10-30 kg
- 1 GeV/c² = 1.783 × 10-27 kg
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, multiply by 11,605 (see Boltzmann constant).
See also: Orders of magnitude
External link