n. (Abbr. J or j)

1. The International System unit of electrical, mechanical, and thermal energy.
2. 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.]

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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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.

[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)]

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.

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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.

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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.

Convert:  Into:  Btu ergs foot-pounds kg-calories kg-meters watt-hrs poundals pounds

Result:

Related measurements:
joules/cm

is short for:

ειδικό πρόγραα έρευνας και τεχνολογικής ανάπτυ_

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).

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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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