Joule (unit)

The joule (symbol: J) is the standard unit of energy and work in the International System of Units. Named after physicist James Prescott Joule, it quantifies the amount of work done when a force of one newton acts over a distance of one meter—or equivalently, the energy dissipated by one watt of power over one second.

The joule appears everywhere in physics. In classical mechanics, it measures kinetic and potential energy. In thermodynamics, it quantifies heat transfer. Electrically, it expresses the energy consumed by appliances. At the smallest scales, it connects to quantum phenomena, though cosmic phenomena operate at scales requiring vastly larger multiples (kilojoules, megajoules, terajoules).

Understanding joules helps demystify everyday experience: a smartphone battery might store 10 megajoules; climbing stairs requires thousands of joules; the renewable energy sector measures solar output in gigajoules daily.

Related

Energy, Power (physics), Force, International System of Units, Thermodynamics, James Prescott Joule