Joule

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The joule (IPA: [dʒuːl] or [dʒaʊl]) (symbol: J) is the SI unit of energy. It was named after James Prescott Joule for his work on the relationship between heat, electricity and mechanical work.

Contents

  • 1 Description
  • 2 History
  • 3 Conversions
    • 3.1 SI multiples
  • 4 See also
  • 5 References
  • 6 External links

[edit] Description

One joule is the work done, or energy expended, by a force of one newton moving an object one metre along the direction of the force. This quantity is also denoted as a Newton-meter with the symbol N·m. Note that torque also has the same units as work, but the quantities are not identical. In elementary units:

1\, \mathrm{J}=1\, \mathrm{kg} \cdot \frac{\mathrm{m}^{2}}{\mathrm{s}^{2}}

One joule is also:

[edit] History

A joule is the mechanical equivalent of heat meaning the number of units of work in which the unit of heat can perform. Its value was found by James Prescott Joule in experiments that showed the mechanical energy Joule's equivalent, and represented by the symbol J. The term was first introduced by Dr. Mayer of Heilbronn.

[edit] Conversions

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

1 joule is exactly 107 ergs.

1 joule is approximately equal to:

Units defined in terms of the joule include:

Useful to remember:

1 joule in everyday life is approximately:

[edit] SI multiples

Multiple Name Symbol Multiple Name Symbol
100 joule J      
101 decajoule daJ 10–1 decijoule dJ
102 hectojoule hJ 10–2 centijoule cJ
103 kilojoule kJ 10–3 millijoule mJ
106 megajoule MJ 10–6 microjoule µJ
109 gigajoule GJ 10–9 nanojoule nJ
1012 terajoule TJ 10–12 picojoule pJ
1015 petajoule PJ 10–15 femtojoule fJ
1018 exajoule EJ 10–18 attojoule aJ
1021 zettajoule ZJ 10–21 zeptojoule zJ
1024 yottajoule YJ 10–24 yoctojoule yJ
This SI unit is named after James Prescott Joule. As for all SI units whose names are derived from the proper name of a person, the first letter of its symbol is uppercase (J). But when an SI unit is spelled out, it should always be written in lowercase (joule), unless it begins a sentence or is the name "degree Celsius".
— Based on The International System of Units, section 5.2.