Joule, << jool or jowl, >> a unit in the metric system of measurement, is used to measure work or energy. Its symbol is J. One joule is the amount of work done when a force of 1 newton acts on an object that moves 1 meter in the direction of the force (see Newton ).
The joule is used to measure all forms of energy, including heat, electrical energy, and mechanical energy. One joule equals about 0.239 calorie. A calorie is the amount of energy needed to raise the temperature of 1 gram of water by 1 Celsius degree. One joule of energy per second is required to pass an electric current of 1 ampere through 1 ohm resistance. One joule per second equals one watt, a unit of electric and mechanical power (see Watt ).
In the inch-pound system of measurement customarily used in the United States, work or energy is measured in foot-pounds. One joule equals about 0.738 foot-pound. The joule was named for the British physicist James P. Joule.
