Source: High school physics (Chinese)
Problem Sets:
Problem
When studying the motion of microscopic particles, the electron-volt (eV) is often used as a unit of energy. 1 eV is the potential energy gained or lost by an electron when it moves through a potential difference of 1 V.
[Q1] $1 \text{ eV} = 1.602 \times 10^{-19}$ J
The change in electric potential energy $\Delta E_p$ is related to the charge $q$ and the potential difference $\Delta U$ by the formula $\Delta E_p = q \Delta U$. For one electron-volt, the charge is the elementary charge $e = 1.602 \times 10^{-19}$ C and the potential difference is $\Delta U = 1$ V.
$$1 \text{ eV} = (1.602 \times 10^{-19} \text{ C})(1 \text{ V})$$Since 1 Joule = 1 Coulomb $\times$ 1 Volt,
$$1 \text{ eV} = 1.602 \times 10^{-19} \text{ J}$$