One electronvolt is the amount of potential energy that one electron in an electric potential field Φ loses when the field Φ is increased by one volt. The potential energy of a charge q in Φ is equal to qΦ. The charge of an electron is −e (minus the elementary charge), so that the energy of the electron in the field is −eΦ. When ΔΦ = 1 volt, the potential energy loss is e, and it follows that in SI units, in which the energy unit joule is coulomb times volt,
- 1 eV = e coulomb × 1 volt = 1.602 176 487 × 10−19 joule.
The loss in potential energy of a single unbound electron that passes in vacuum through an electric potential difference of 1 volt is the increase in its kinetic energy (provided radiation damping is negligible).
- J. D. Jackson, Classical Electrodynamics,John Wiley, New York, 2nd ed. (1975). p. 45
- Value of e retrieved from Physics Today on September 19, 2009