Electronvolt (eV)
The electronvolt, symbolized as eV, is primarily used in atomic, nuclear, and particle physics. It is the energy gained by an electron moving through a one-volt potential. The electronvolt enables scientists to measure very small energy changes at the atomic scale. Introduced in the early 20th century, it is standard for describing energy in atoms, photons, and particles. The electronvolt adds the necessary precision in modern physics and works in conjunction with larger units, such as joules and kilojoules.
Kilojoule (kJ)
The kilojoule, symbol kJ, equals 1,000 joules and is used for measuring larger quantities of energy. It was introduced to simplify calculations in nutrition, physics, and engineering, where joules alone would result in very large numbers. Kilojoules are commonly used to express the energy content of foods, fuel consumption, and industrial energy usage. The adoption of the kilojoule has standardized energy measurements across scientific disciplines and commercial applications, offering clarity and ease of use in both everyday and professional contexts.