Voltette

Meet Voltette, an electron who gains one electronvolt of energy by crossing one volt.

An electronvolt is the energy an electron gains when it moves through a potential difference of one volt. Since energy equals charge times voltage, one electronvolt equals the elementary charge times one volt, 1.602 × 10⁻¹⁹ J.

Since 2019, the elementary charge has had an exact value in SI, 1.602176634 × 10⁻¹⁹ C, so the electronvolt is exactly 1.602176634 × 10⁻¹⁹ J.

The joule is far too large for single particles, so physicists use electronvolts. Photons of visible light carry about 1.8 to 3.1 eV. The typical thermal energy of a molecule at room temperature, kT, is only about 0.025 eV. The energy needed to remove the electron from a hydrogen atom is 13.6 eV.

Particle physics uses millions and billions of them. The rest energy of a proton is about 938 MeV, and the Large Hadron Collider accelerates protons to several trillion electronvolts. Despite the name, the unit can measure the energy of any particle, not just electrons.