When an electron is accelerated by 1 volt, it gains (or loses) energy equal to 1 electron volt (eV). The electron volt is a unit of energy commonly used in atomic and particle physics.
By definition, 1 electron volt is the amount of energy gained (or lost) by an electron when it is accelerated through an electric potential difference of 1 volt. The value of an electron volt in joules is approximately 1.602 × 10^−19 J.
So, if an electron is accelerated by 1 volt, it gains (or loses) an energy of approximately 1.602 × 10^−19 joules (or 1 eV).