In
physics, the
electronvolt (symbol
eV; also written
electron volt) is a
unit of energy equal to approximately 160 zeptojoules (symbol zJ) or
joules (symbol J). By definition, it is the amount of energy gained (or lost) by the charge of a single
electron moved across an
electric potential difference of one
volt. Thus it is 1
volt (1 joule per
coulomb, ) multiplied by the
elementary charge (
e, or
[1]{physconst|e}}). Therefore, one electron volt is equal to Historically, the electron volt was devised as a standard unit of measure through its usefulness in electrostatic particle accelerator sciences because a particle with charge
q has an energy after passing through the potential
V; if
q is quoted in integer units of the elementary charge and the terminal bias in volts, one gets an energy in eV.
