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In physics, the electron volt (symbol eV; also written electronvolt) is a unit of energy equal to approximately 1.6×10^?19 joule (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, 1 J/C) multiplied by the negative of the electron charge (?1 e, or ?1.602176565(35)×10^?19 C). Therefore, one electron volt is equal to 1.602176565(35)×10^?19 J.