joule

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Dictionary: joule (jūl, joul) pronunciation

n. (Abbr. J or j)

The International System unit of electrical, mechanical, and thermal energy.
1. A unit of electrical energy equal to the work done when a current of one ampere is passed through a resistance of one ohm for one second.
2. A unit of energy equal to the work done when a force of one newton acts through a distance of one meter.

[After James Prescott JOULE.]

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5min Related Video: Kilojoule

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Chemistry Dictionary: joule

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Symbol J. The SI unit of work and energy equal to the work done when the point of application of a force of one newton moves, in the direction of the force, a distance of one metre. 1 joule=10⁷ ergs=0.2388 calorie. It is named after James Prescott Joule.

Computer Desktop Encyclopedia: joule

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A unit of energy in the MKS system. It is equal to 10,000,000 ergs in the CGS system. Surge protectors are often given joule ratings, but this refers only to the amount of energy they can absorb, not what gets through. See CGS system.

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Food and Fitness: joule

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Unit of energy; approximately 4.2 joules (J) equal one calorie. One kilojoule (kJ) equals 1000 J and is the amount of heat required to raise the temperature of 239 g of water by 1°C; and 1 megajoule (MJ) equals 1000 kJ.

Measures and Units: joule

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[Etymology: J. P. Joule; UK 1818-89] energy, work, quantity of heat. Symbol J. The joules of work done by a steady current equal the product of the number of coulombs of charge and the electromotive force in volts. J = C·V.

SI, Metric-m.k.s. A. Also = N·m (= m²·kg·s^-2 in base terms). The following are among the coherent derived units:

• J·m^-3 for energy density;
• J·kg^-1 for specific energy;
• J·kg^-1 = gray for absorbed radiation;
• J·kg^-1 = sievert for dose equivalent;
• J·s^-1 = watt for power, radiant flux;
• J·K^-1 for entropy, heat capacity;
• J·mol^-1 for molar energy;
• J·mol^-1·K^-1 for molar entropy or molar heat capacity;
• J·V^-1 = coulomb for quantity of electricity;
• J·C^-1 = volt for electromotive force, potential difference;
• J·kg^-1·K^-1 for specific entropy or specific heat capacity.

See also practical unit.

History

The joule was recognized internationally in 1889, at the second International Electrical Conference, as a derived addition to the practical units of the c.g.s. system; it was defined as the energy dissipated in 1 second by current of 1 ampere flowing through a resistance of 1 ohm. Hence the practical joule. While discrepancies, for the underlying ampere and ohm, between measured absolute values (in centimetre-gram-second terms) and their laboratory specifications led the IEC in 1908 to rename units based on the latter as unadorned international units, differing by 0.05~ % from the practical, the joule as a mechanical unit was unequivocally a force of 10⁷ dyne acting over 1 centimetre (= 10⁷ erg).

With the implementation of the m.k.s.A. system in 1948, this became 1 newton acting over 1 metre (leaving its electric definition unchanged). The same year, the joule was accepted as a unit of heat; prior to this, and despite the initial electric definition of 1889 using the expression ‘the energy disengaged as heat in one second’, the joule was regarded as a mechanical equivalent of, but not a measure of heat.

1946

CIPM ‘Joule (unit of work or energy) The joule is the work done when the point of application of 1 MKS unit of force [newton] moves a distance of 1 metre in the direction of the force.’see note below

[Le Système International d'Unités (Sèvres, France: Bureau International de Poids et Mesures, 1985)]

Architecture: joule

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A unit of energy or work; equals the work done by a force of 1 newton which acts over a distance of 1 metre in the direction of the force.

Sports Science and Medicine: joule

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The derived SI unit of work or energy. One joule is the amount of work done when the point of application of a force of 1 newton is displaced through a distance of one metre in the direction of the force. One joule is equivalent to 0.239 cal.

Columbia Encyclopedia: joule

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joule (jūl, joul), abbr. J, unit of work or energy in the mks system of units, which is based on the metric system; it is the work done or energy expended by a force of 1 newton acting through a distance of 1 meter. The joule is named for James P. Joule.

Unit Conversions: joules

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To convert from joules to:

Btu, multiply by 9.48E-04.
ergs, multiply by 10000000.
foot-pounds, multiply by .7376.
kg-calories, multiply by .0002389.
kg-meters, multiply by .102.
watt-hrs, multiply by .0002778.
poundals, multiply by 723.3.
pounds, multiply by 22.48.

Related measurements:
joules/cm

Word Tutor: joule

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IN BRIEF: n. - A unit of electrical energy equal to the work done when a current of one ampere passes through a resistance of one ohm for one second.

Tutor's tip: A "jewel" is a (precious stone), a "joule" is (a measure of energy in physics). Do not confuse these with "jowl" which refers to (the jaw and the loose skin of the throat).

Wikipedia: Joule

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This article is about the unit of energy. For other uses, see Joule (disambiguation).

Joule
Standard:	SI derived unit
Quantity:	Energy
Symbol:	J
Named after:	James Prescott Joule
Expressed in:	1 J =
SI base units	1 kg·m²/s²
CGS units	1×10⁷ erg

The joule (symbol J), named for James Prescott Joule, is the derived unit of energy in the International System of Units. It is the energy exerted by a force of one newton acting to move an object through a distance of one metre. In terms of dimensions:

$\rm 1\ J = 1\ N \cdot m = \left ( \frac{kg \cdot m}{s^2} \right ) \cdot m = \frac{kg \cdot m^2}{s^2}=Pa \cdot m^3= 1\ W \cdot s$

1 Definition
- 1.1 Usage
2 Confusion with newton metre
3 Practical examples
4 Multiples
5 Conversions
6 See also
7 References
8 External links

Definition

One joule is defined as the amount of work done by a force of one newton moving an object through a distance of one metre. Other relationships are:

The work required to move an electric charge of one coulomb through an electrical potential difference of one volt; or one coulomb volt (C·V). This relationship can be used to define the volt;
The work required to continuously produce one watt of power for one second; or one watt second (W·s) (compare kilowatt hour). This relationship can be used to define the watt.

Usage

This SI unit is named after James Prescott Joule. As with every SI unit whose name is derived from the proper name of a person, the first letter of its symbol is uppercase (J). When an SI unit is spelled out in English, it should always begin with a lowercase letter (joule), except where any word would be capitalized, such as at the beginning of a sentence or in capitalized material such as a title. Note that "degree Celsius" conforms to this rule because the "d" is lowercase.

—Based on The International System of Units, section 5.2.

Confusion with newton metre

Main article: Newton metre

While it is dimensionally correct to express joules as newton metres or N·m, such use is discouraged^[1] by the SI authority to avoid confusion with torque. Torque and energy are fundamentally different physical quantities. For example, adding 1 N·m of torque to 1 N·m of energy gives a dimensionally consistent result of 2 N·m, but this quantity is physically meaningless.

Practical examples

One joule in everyday life is approximately:

the energy required to lift a small apple one meter straight up.
the energy released when that same apple falls one meter to the ground.
the energy released as heat by a person at rest, every hundredth of a second.
the energy required to heat one gram of dry, cool air by 1 degree Celsius.
one hundredth of the energy a person can receive by drinking a drop of beer.
the kinetic energy of an adult human moving at a speed of about a handspan every second.
the kinetic energy of a tennis ball moving at 23 km/h (14 mph).^[2]

Multiples

For additional examples, see: Orders of magnitude (energy)

SI multiples for joule (J)
Value	Symbol	Name	Value	Symbol	Name
Submultiples			Multiples
10^–1 J	dJ	decijoule	10¹ J	daJ	decajoule
10^–2 J	cJ	centijoule	10² J	hJ	hectojoule
10^–3 J	mJ	millijoule	10³ J	kJ	kilojoule
10^–6 J	µJ	microjoule	10⁶ J	MJ	megajoule
10^–9 J	nJ	nanojoule	10⁹ J	GJ	gigajoule
10^–12 J	pJ	picojoule	10¹² J	TJ	terajoule
10^–15 J	fJ	femtojoule	10¹⁵ J	PJ	petajoule
10^–18 J	aJ	attojoule	10¹⁸ J	EJ	exajoule
10^–21 J	zJ	zeptojoule	10²¹ J	ZJ	zettajoule
10^–24 J	yJ	yoctojoule	10²⁴ J	YJ	yottajoule
Common multiples are in bold face

Nanojoule

The nanojoule (nJ) is equal to one billionth of one joule. One nanojoule is about 1/160th of the kinetic energy of a flying mosquito.^[3]

Microjoule

The microjoule (μJ) is equal to one millionth of one joule. The Large Hadron Collider (LHC) is expected to produce collisions on the order of 1 microjoule (7 Tev) per particle.

Millijoule

The millijoule (mJ) is equal to one thousandth of one joule.

Kilojoule

The kilojoule (kJ) is equal to one thousand joules. Food labels in some countries express food energy in kilojoules. One kilojoule is about the amount of solar radiation received by one square metre of the Earth in one second.^[4]

Megajoule

The megajoule (MJ) is equal to one million joules, or approximately the kinetic energy of a one tonne vehicle moving at 160 km/h (100 mph).

Gigajoule

The gigajoule (GJ) is equal to one billion joules. 6 gigajoules is about the amount of chemical energy in a standard barrel of oil.^[5]

Terajoule

The terajoule (TJ) is equal to one trillion joules. About 60 terajoules were released by the bomb that exploded over Hiroshima.^[6]

Conversions

Main article: Conversion of units#Energy, work, or amount of heat

1 joule is equal to:

1×10⁷ ergs (exactly)
6.24150974×10¹⁸ eV (electronvolts)
0.2390 cal (thermochemical gram calories or small calories)
2.3901×10⁻⁴ kcal (thermochemical kilocalories, kilogram calories, large calories or food calories)
9.4782×10⁻⁴ BTU (British thermal unit)
0.7376 ft·lbf (foot-pound force)
23.7 ft·pdl (foot-poundals)
2.7778×10⁻⁷ kilowatt-hour
2.7778×10⁻⁴ watt-hour
9.8692×10⁻³ liter-atmosphere
1×10⁻⁴⁴ Foe (exactly)

Units defined exactly in terms of the joule include:

1 thermochemical calorie = 4.184 J^[7]
1 International Table calorie = 4.1868 J^[7]
1 watt hour = 3600 J
1 kilowatt hour = 3.6×10⁶ J (or 3.6 MJ)
1 ton TNT = 4.184 GJ

References

^ From the official SI website: "A derived unit can often be expressed in different ways by combining base units with derived units having special names. Joule, for example, may formally be written newton metre, or kilogram metre squared per second squared. This, however, is an algebraic freedom to be governed by common sense physical considerations; in a given situation some forms may be more helpful than others. In practice, with certain quantities, preference is given to the use of certain special unit names, or combinations of unit names, to facilitate the distinction between different quantities having the same dimension."
^ Ristinen, Robert A., and Jack J. Kraushaar. Energy and the Environment. 2nd ed. Hoboken, NJ: John Wiley & Sons, Inc., 2006.
^ CERN - Glossary
^ "Construction of a Composite Total Solar Irradiance (TSI) Time Series from 1978 to present". http://www.pmodwrc.ch/pmod.php?topic=tsi/composite/SolarConstant. Retrieved 2005-10-05.
^ IRS publication
^ Los Alamos National Laboratory report LA-8819, The yields of the Hiroshima and Nagasaki nuclear explosions by John Malik, September 1985. Available online at http://www.mbe.doe.gov/me70/manhattan/publications/LANLHiroshimaNagasakiYields.pdf
^ ^a ^b The adoption of joules as units of energy, FAO/WHO Ad Hoc Committee of Experts on Energy and Protein, 1971. A report on the changeover from calories to joules in nutrition.

External links

Unit conversion from joule

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Translations: Joule

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Dansk (Danish)
n. - joule, kalorie, wattsekund

Nederlands (Dutch)
joule

Français (French)
n. - joule

Deutsch (German)
n. - Joule

Ελληνική (Greek)
n. - (φυσ.) (μονάδα) τζάουλ

Italiano (Italian)
joule (unità di energia)

Português (Portuguese)
n. - joule (m) (medida de energia) (Fís.)

Русский (Russian)
джоуль

Español (Spanish)
n. - julio, joule

Svenska (Swedish)
n. - joule

中文（简体）(Chinese (Simplified))
焦耳

中文（繁體）(Chinese (Traditional))
n. - 焦耳

한국어 (Korean)
n. - 에너지의 단위

日本語 (Japanese)
n. - ジュール

العربيه (Arabic)
‏(الاسم) جول ( وحدة طاقه كهربائيه)‏

עברית (Hebrew)
n. - ‮ג'אול (יחידת אנרגיה/עבודה)‬

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