joule

The joule (symbol: J) is the derived unit of energy in the International System of Units (SI). It is named after the English physicist James Prescott Joule. One joule is equal to the work done (or energy expended) by a force of one newton acting over a distance of one meter in the direction of the force. Mathematically, it is defined as 1 J = 1 kg·m²/s².

The joule is used to measure various forms of energy, including mechanical, electrical, and thermal energy. In electrical systems, one joule is the energy transferred when one ampere of current flows for one second under the influence of one volt. In thermodynamics, one joule is the amount of heat required to raise the temperature of one gram of water by 0.239 degrees Celsius.

The joule is a coherent derived unit in the SI with a special name and symbol. It is also used as a unit of work, heat, or energy. The kilojoule (kJ), megajoule (MJ), and gigajoule (GJ) are commonly used larger multiples of the joule. The joule is also used in the definition of other SI units, such as the watt (1 W = 1 J/s) and the newton (1 N = 1 J/m).