Joule

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The joule (symbol J) 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. Algebraically:

Contents 1 Definition 2 Conversions 2.1 Practical examples 2.2 SI multiples 3 See also 4 References 5 External links

[edit] Definition

One joule is the amount of energy required to perform the following physical actions:

• The work done by a force of one newton travelling through a distance of one metre;
• The work required to move an electric charge of one coulomb through an electrical potential difference of one volt; or one coulomb volt, with the symbol C·V;
• The work done to produce the power of one watt continuously for one second; or one watt second (compare kilowatt hour), with the symbol W·s.

[edit] Conversions

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 litre-atmosphere
• 1×10⁻⁴⁴ Foe (exactly)

Units defined in terms of the joule include:

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

Useful to remember:

• 1 joule = 1 newton × 1 metre = 1 watt × 1 second

[edit] Practical examples

One joule in everyday life is approximately:

• the energy required to lift a small apple 20 cm straight up.
• the energy released when that same apple falls 20cm to the ground.
• the energy released as heat by a quiet person, every 0.20 seconds.
• 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 a distance of about a handspan every second.

[edit] SI multiples

SI multiples for joule (J)

Submultiples				Multiples
Value	Symbol	Name		Value	Symbol	Name
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

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.

[edit] See also

• Conversion of units
• Orders of magnitude (energy)
• Fluence

[edit] References

• 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.

[edit] External links

• Unit conversion from joule
• Online Joule Converter
• Joule in E=mc²