Joule: Difference between revisions
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The '''joule''' (symbol = '''J''') is the [[SI]] unit of [[Energy|energy]]. One joule equals equals the work done (or energy expended) by a force of one [[newton]] (symbol = '''N''') acting over a distance of one meter (symbol = '''m'''). One newton equals a force that produces an acceleration of one meter per second per second on a one kilogram (kg) mass. Therefore, one joule equals one newton•meter. One joule also measures the energy released by an electric charge of one [[coulomb]] dropping one [[volt]] in electrical potential. | ::''Note: Text in font-color <font color=#0000FF>blue</font> links to articles in Citizendium; text in font-color <font color=#006600>green</font> links to articles not yet started (authors/editors encouraged to initiate such articles)'' | ||
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The '''joule''' (symbol = '''J''') is the [[SI]] unit of [[Energy|energy]] — a measure of the capacity to do [[Work|work]] or generate [[Heat|heat]]. One joule equals equals the work done (or energy expended) by a force of one [[newton]] (symbol = '''N''') acting over a distance of one meter (symbol = '''m'''). One newton equals a force that produces an acceleration of one meter per second per second on a one kilogram (kg) mass. Therefore, one joule equals one newton•meter. One joule also measures the energy released by an electric charge of one [[coulomb]] dropping one [[volt]] in electrical potential. | |||
In terms of SI basic units: | In terms of SI basic units: | ||
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The joule is named for [[James Prescott Joule]] (1818 - 1889), who studied the relation between mechanical and heat energy discovered earlier by [[count Rumford]]. | The joule is named for [[James Prescott Joule]] (1818 - 1889), who studied the relation between mechanical and heat energy discovered earlier by [[count Rumford]]. | ||
==Other units of energy convertible to joules== | |||
Whereas the joule is the standard SI unit of energy, many other units of energy, all convertible to joules, are used in particular circumstances. Those include: [[Erg|erg]]; [[Foot pound|foot pound]]; [[Watt second|watt second]]; [[Watt hour|watt hour]]; [[Kilowatt hour|kilowatt hour]]; [[Thermochemical calorie|thermochemical calorie]]; [[International Table calorie]]; [[Kilocalorie|kilocalorie]]; [[Thermochemical Btu|thermochemical Btu]]; [[Therm|therm]]; [[Quad|quad]]; [[Cubic meter natural gas|cubic meter natural gas]]; [[Ton of oil equivalent|ton of oil equivalent]]; [[Ton of coal equivalent|ton of coal equivalent]]; [[Ton of TNT|ton of TNT]]; [[Electron volt|electron volt]]; [[Hartree|hartree]]; [[Inverse meter|inverse meter]]; [[Inverse second|inverse second]]; [[Kelvin|kelvin]]; [[Kilogram|kilogram]].<ref name=elert>Elert G. (1998-2008) [http://hypertextbook.com/physics/mechanics/energy/ Energy: The Physics Hypertextbook™. A Work in Progress.] Fair Use Encouraged.</ref> One kilogram of mass is equivalent to exactly 89,875,517,873,681,764 joules.<ref name=elert/> | |||
==Practical use== | ==Practical use== | ||
Revision as of 21:23, 25 June 2008
- Note: Text in font-color blue links to articles in Citizendium; text in font-color green links to articles not yet started (authors/editors encouraged to initiate such articles)
The joule (symbol = J) is the SI unit of energy — a measure of the capacity to do work or generate heat. One joule equals equals the work done (or energy expended) by a force of one newton (symbol = N) acting over a distance of one meter (symbol = m). One newton equals a force that produces an acceleration of one meter per second per second on a one kilogram (kg) mass. Therefore, one joule equals one newton•meter. One joule also measures the energy released by an electric charge of one coulomb dropping one volt in electrical potential.
In terms of SI basic units:
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'Joule' is variously pronounced 'jool' (rhymes with 'jewel') or 'joul' (rhymes with 'jowl').
The amount of energy delivered by a one watt source of power in one second is one Joule. The joule is also used to measure thermal energy. One calorie of heat is the equivalent of 4.186 J.
The joule is named for James Prescott Joule (1818 - 1889), who studied the relation between mechanical and heat energy discovered earlier by count Rumford.
Other units of energy convertible to joules
Whereas the joule is the standard SI unit of energy, many other units of energy, all convertible to joules, are used in particular circumstances. Those include: erg; foot pound; watt second; watt hour; kilowatt hour; thermochemical calorie; International Table calorie; kilocalorie; thermochemical Btu; therm; quad; cubic meter natural gas; ton of oil equivalent; ton of coal equivalent; ton of TNT; electron volt; hartree; inverse meter; inverse second; kelvin; kilogram.[1] One kilogram of mass is equivalent to exactly 89,875,517,873,681,764 joules.[1]
Practical use
- A baseball pitched by a fast Major League pitcher has a kinetic energy of approximately 230 J.
- One "dietary calorie" (as used in the United States to designate a kilocalorie) is 4186 J (4.186 kJ).
- One gram of gasoline releases about 50 kJ on combustion in air.
- A small car (about 1200 kg) travelling at 65 miles per hour (105 km/h) has a kinetic energy of 1 megajoule (1 MJ).
- One "kilowatt-hour" is 3.6 MJ.
- One ton of TNT releases 4.184 GJ on exploding.
- ↑ 1.0 1.1 Elert G. (1998-2008) Energy: The Physics Hypertextbook™. A Work in Progress. Fair Use Encouraged.