joul

n. [ From the distinguished English physicist, James Prescott Joule (1818-1889). ] (Physics.) A unit of work which is equal to 107 ergs (the unit of work in the C. G. S. system of units), and is equivalent to one watt-second, the energy expended in one second by an electric current of one ampere in a resistance of one ohm; also called the absolute joule. It is abbreviated J or j. The international joule is slightly larger, being 1.000167 times the absolute joule. The absolute joule is approximately equal to 0.737562 foot pounds, 0.239006 gram-calories (small calories), and 3.72506 x 10-7 horsepower-hours, and 0.000948451 B.t.u. HCP61 [ 1913 Webster +PJC ]

Joule's equivalent. See under Equivalent, n. [ 1913 Webster ]

n. An integrating wattmeter for measuring the energy in joules expended in an electric circuit or developed by a machine. [ Webster 1913 Suppl. ]

(Thermodynamics) The cycle for the air engine proposed by Joule. In it air is taken by a pump from a cold chamber and compressed adiabatically until its pressure is eqal to that of the air in a hot chamber, into which it is then delivered, thereby displacing an equal amount of hot air into the engine cylinder. Here it expands adiabatically to the temperature of the cold chamber into which it is finally exhausted. This cycle, reversed, is used in refrigerating machines. [ Webster 1913 Suppl. ]