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  • Joule

    Joule

    • Joule
      Unit system SI derived unit
      Unit of Energy
      Symbol J 
      Named after James Prescott Joule
      1 J in ... ... is equal to ...
         SI base units    kgm2s−2
         CGS units    1×107 erg
         kilowatt hours    2.78×10−7 kW⋅h
         kilocalories (thermochemical)    2.390×10−4 kcalth
         BTUs    9.48×10−4 BTU
         electronvolts    6.24×1018 eV
      SI multiples for joule (J)
      Submultiples Multiples
      Value SI symbol Name Value SI 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

      The joule (/ˈl/), symbol J, is a derived unit of energy in the International System of Units. It is equal to the energy transferred to (or work done on) an object when a force of one newton acts on that object in the direction of its motion through a distance of one metre (1 newton metre or N·m). It is also the energy dissipated as heat when an electric current of one ampere passes through a resistance of one ohm for one second. It is named after the English physicist James Prescott Joule (1818–1889).

      In terms firstly of base SI units and then in terms of other SI units:

      where kg is the kilogram, m is the metre, s is the second, N is the newton, Pa is the pascal, W is the watt, C is the coulomb, and V is the volt.

      One joule can also be defined as:

      This SI unit is named after James Prescott Joule. As with every International System of Units (SI) unit named for a person, the first letter of its symbol is upper case (J). However, when an SI unit is spelled out in English, it should always begin with a lower case letter (joule)—except in a situation where any word in that position would be capitalized, such as at the beginning of a sentence or in material using title case. Note that "degree Celsius" conforms to this rule because the "d" is lowercase.— Based on The International System of Units, section 5.2.


      Linear Angular
      force torque
      mass moment of inertia
      distance angle
      SI multiples for joule (J)
      Submultiples Multiples
      Value SI symbol Name Value SI 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

      For additional examples, see: Orders of magnitude (energy)
      • The energy required to lift a medium-size tomato (100 g) 1 meter vertically from the surface of the Earth.
      • The energy released when that same tomato falls back down to the ground.
      • The energy required to accelerate a 1 kg mass at 1 m·s−2 through a 1 m distance in space.
      • The heat required to raise the temperature of 1 g of water by 0.24 °C.
      • The typical energy released as heat by a person at rest every 1/60 second (approximately 17 ms).
      • The kinetic energy of a 50 kg human moving very slowly (0.2 m/s or 0.72 km/h).
      • The kinetic energy of a 56 g tennis ball moving at 6 m/s (22 km/h).
      • The kinetic energy of an object with mass 1 kg moving at √2 ≈ 1.4 m/s.
      • The amount of electricity required to light a 1 watt LED for 1 s.
      • 1×107 erg (exactly)
      • 6.24150974×1018 eV
      • 0.2390 cal (gram calories)
      • 2.390×10−4 kcal (food calories)
      • 9.4782×10−4 BTU
      • 0.7376 ft·lb
      • 23.7 ft·pdl (foot-poundal)
      • 2.7778×10−7 kilowatt-hour
      • 2.7778×10−4 watt-hour
      • 9.8692×10−3 l·atm (litre-atmosphere)
      • 11.1265×10−15 gram (by way of mass-energy equivalence)
      • 1×10−44 foe (exactly)
      • 1 thermochemical calorie = 4.184 J
      • 1 International Table calorie = 4.1868 J
      • 1 watt hour = 3600 J (or 3.6 kJ)
      • 1 kilowatt hour = 3.6×106 J (or 3.6 MJ)
      • 1 watt second = 1 J
      • 1 ton TNT = 4.184 GJ
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