|
|
| Line 1: |
Line 1: |
| {{About| the unit of energy}}
| | Friends contact him Royal. Interviewing is what she does in her working day occupation but soon her spouse and her will begin their personal company. What she enjoys doing is bottle tops gathering and she is trying to make it a profession. My home is now in Kansas.<br><br>My weblog - extended auto warranty ([http://xn--pappasker-57A.se/sarister additional resources]) |
| {{Infobox Unit
| |
| | bgcolour =
| |
| | name = Joule
| |
| | image =
| |
| | caption =
| |
| | standard = [[SI derived unit]]
| |
| | quantity = [[Energy]]
| |
| | symbol = J
| |
| | dimension = M⋅L<sup>2</sup>⋅T<sup>−2</sup>
| |
| | namedafter = [[James Prescott Joule]]
| |
| | units1 = [[SI base unit]]s
| |
| | inunits1 = 1 [[kilogram|kg]]·[[metre|m]]<sup>2</sup>/[[second|s]]<sup>2</sup>
| |
| | units2 = [[CGS unit]]s
| |
| | inunits2 = {{val|1|e=7}} [[erg]]
| |
| | units3 = [[kilowatt hour]]s
| |
| | inunits3 = {{val|2.78|e=-7|u=kW·h}}
| |
| | units4 = [[kilocalorie]]s
| |
| | inunits4 = {{val|2.39|e=-4|u=kcal}}
| |
| | units5 = [[British thermal unit|BTU]]s
| |
| | inunits5 = {{val|9.48|e=-4|u=BTU}}
| |
| | units6 = [[electronvolt]]s
| |
| | inunits6 = {{val|6.24|e=18|u=eV}}
| |
| }}
| |
| The '''joule''' ({{IPAc-en|ˈ|dʒ|uː|l}} or sometimes {{IPAc-en|ˈ|dʒ|aʊ|l}}), symbol '''J''', is a [[SI derived unit|derived unit]] of [[energy]], [[Work (physics)|work]], or amount of [[heat]] in the [[International System of Units]].<ref>{{SIbrochure8th|page=120}}</ref> It is equal to the energy expended (or work done) in applying a [[force]] of one [[Newton (unit)|newton]] through a distance of one [[metre]] (1 newton metre or N·m), or in passing an electric [[current (electricity)|current]] of one [[ampere]] through a [[resistance (electricity)|resistance]] of one [[ohm]] for one second. It is named after the English physicist [[James Prescott Joule]] (1818–1889).<ref>[http://education.yahoo.com/reference/dictionary/entry/joule American Heritage Dictionary of the English Language], Online Edition (2009). Houghton Mifflin Co., hosted by [http://education.yahoo.com/ Yahoo! Education].</ref><ref>''The American Heritage Dictionary'', Second College Edition (1985). Boston: Houghton Mifflin Co., p. 691.</ref><ref>''McGraw-Hill Dictionary of Physics'', Fifth Edition (1997). McGraw-Hill, Inc., p. 224.</ref>
| |
| | |
| In terms firstly of base [[International System of Units|SI units]] and then in terms of other SI units:
| |
| :<math>\rm J = {}\rm \frac{kg \cdot m^2}{s^2} = N \cdot m = \rm Pa \cdot m^3={}\rm W \cdot s = C \cdot V</math>
| |
| | |
| where kg is the [[kilogram]], m is the [[metre]], s is the [[second]], N is the [[newton (unit)|newton]], Pa is the [[pascal (unit)|pascal]], W is the [[watt]], C is the [[coulomb (unit)|coulomb]], and V is the [[volt]].
| |
| | |
| One joule can also be defined as:
| |
| * The work required to move an [[electric charge]] of one [[coulomb]] through an [[Voltage|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 produce one [[watt]] of [[Power (physics)|power]] for one [[second]], or one "watt second" (W·s) (compare [[kilowatt hour]]). This relationship can be used to define the watt.
| |
| | |
| ==Usage==
| |
| {{SI unit lowercase|James Prescott Joule|joule|J}}
| |
| | |
| ==Confusion with newton-metre==
| |
| {{Main|newton metre}}
| |
| In [[Rotation around a fixed axis|angular mechanics]], torque is analogous to the linear [[Newtonian mechanics]] parameter of force, [[moment of inertia]] to [[mass]], and [[Angular distance|angle]] to distance. Energy is the same in both systems. Thus, although the joule has the same dimensions as the newton-meter (1 J = 1 N·m = 1 kg·m<sup>2</sup>·s<sup>−2</sup>), these units are ''not'' interchangeable: the [[CGPM]] has given the unit of [[energy]] the name "joule", but has not given the unit of [[torque]] any special name, hence the unit of torque is known as the newton-metre (N·m) - a compound name derived from its constituent parts.<ref name=BIPM2>From the [http://www.bipm.org/en/si/si_brochure/chapter2/2-2/2-2-2.html 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."</ref> Torque and energy are related to each other using the equation
| |
| :<math>E= \tau \theta\ </math>
| |
| where ''E'' is the energy, ''τ'' is the torque, and ''θ'' is the angle moved (in [[radian]]s). Since radians are dimensionless, it follows that torque and energy have the same dimensions.
| |
| | |
| The use of newton-metres for torque and joules for energy is useful in helping avoid misunderstandings and miscommunications.<ref name=BIPM2/> Another solution to this problem is to name the unit of angle, such that the unit of torque is called joule per radian.
| |
| | |
| == Practical examples ==
| |
| One joule in everyday life represents approximately:
| |
| * the energy required to lift a small apple (with a mass of approximately 100 g) vertically through one meter.
| |
| * the energy released when that same apple falls one meter to the ground.
| |
| * the heat required to raise the temperature of 1 g of water by 0.24 K.<ref>{{cite web|url=http://www.engineeringtoolbox.com/heat-units-d_664.html |title=Units of Heat - BTU, Calorie and Joule |publisher=Engineeringtoolbox.com |date= |accessdate=2013-09-16}}</ref>
| |
| * the typical energy released as [[heat]] by a person at rest, every 1/60th of a second.<ref>This is called the [[basal metabolic rate]]. It corresponds to about 1200 [[kilocalorie]]s (also called [[calorie|dietary calorie]]s) per day. "At rest" means awake but inactive.</ref>
| |
| * the [[kinetic energy]] of a 50 kg human moving very slowly (0.2 m/s).
| |
| * the kinetic energy of a tennis ball moving at 23 km/h (6.4 m/s).<ref>{{cite book |last=Ristinen |first=Robert A. |first2=Jack J. |last2=Kraushaar |title=Energy and the Environment |edition=2nd |location=Hoboken, NJ |publisher=John Wiley & Sons |year=2006 |isbn=0-471-73989-8 }}</ref>
| |
| * the kinetic energy of 1 kg moving √2 m/s.
| |
| Since the joule is also a watt-second and the common unit for electricity sales to homes is the kWh (kilowatt-hour), a kWh is thus 1000 (kilo) x 3600 seconds = 3.6 MJ (megajoules).
| |
| | |
| ==Multiples==
| |
| :''For additional examples, see: [[Orders of magnitude (energy)]]''
| |
| {|class=infobox
| |
| |-
| |
| |{{SI multiples
| |
| |unit=joule
| |
| |symbol=J
| |
| |note=Common multiples are in bold face
| |
| |m=|k=|mc=|M=|n=|G=|p=|T=
| |
| }}
| |
| |}
| |
| | |
| ===Nanojoule===
| |
| The nanojoule (nJ) is equal to one billionth of one joule. One nanojoule is about 1/160 of the [[kinetic energy]] of a flying mosquito.<ref>[http://public.web.cern.ch/Public/en/Science/Glossary-en.php CERN - Glossary]</ref>
| |
| | |
| ===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 [[electron volt|TeV]]) per particle.
| |
| | |
| ===Millijoule===
| |
| The millijoule (mJ) is equal to one thousandth of a joule.
| |
| | |
| ===Kilojoule===
| |
| The kilojoule (kJ) is equal to one thousand (10<sup>3</sup>) joules. Nutritional food labels in certain countries express energy in standard kilojoules (kJ).
| |
| | |
| One kilojoule per second (1000 watts) is approximately the amount of [[sunlight#Solar constant|solar radiation]] received by one square metre of the [[Earth]] in full daylight.<ref name=TSI>{{cite web |title=Construction of a Composite Total Solar Irradiance (TSI) Time Series from 1978 to present |url=http://www.pmodwrc.ch/pmod.php?topic=tsi/composite/SolarConstant | accessdate = 2005-10-05}}</ref>
| |
| | |
| ===Megajoule===
| |
| The megajoule (MJ) is equal to one million (10<sup>6</sup>) joules, or approximately the kinetic energy of a one-[[ton]] vehicle moving at 160 km/h (100 mph).
| |
| | |
| Because 1 watt times one second equals one joule, 1 [[kilowatt-hour]] is 1000 watts times 3600 seconds, or 3.6 megajoules.
| |
| | |
| ===Gigajoule===
| |
| The gigajoule (GJ) is equal to one billion (10<sup>9</sup>) joules. Six gigajoules is about the amount of potential [[chemical energy]] in a [[Barrel of oil equivalent|barrel]] of oil, when combusted.<ref>[http://www.irs.gov/pub/irs-drop/n-99-18.pdf IRS publication]</ref>
| |
| | |
| ===Terajoule===
| |
| The terajoule (TJ) is equal to one trillion (10<sup>12</sup>) joules. About 63 terajoules were released by [[Little Boy|the atomic bomb that exploded over Hiroshima]].<ref>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</ref> The [[International Space Station]], with a mass of approximately 450,000 kg and orbital velocity of 7.7 km/s,<ref>[http://www.spaceflight.esa.int/users/downloads/factsheets/fs001_12_iss.pdf International Space Station Fact Sheet]</ref> has a [[kinetic energy]] of roughly 13.34 terajoules.
| |
| | |
| ===Petajoule===
| |
| The petajoule (PJ) is equal to one quadrillion (10<sup>15</sup>) joules. 210 PJ is equivalent to about 50 megatons of TNT. This is the amount of energy released by the [[Tsar Bomba]], the largest man-made nuclear explosion ever.
| |
| | |
| ===Exajoule===
| |
| The exajoule (EJ) is equal to one quintillion (10<sup>18</sup>) joules. The [[2011 Tōhoku earthquake and tsunami]] in Japan had 1.41 EJ of energy according to its 9.0 on the [[moment magnitude scale]]. [[Energy in the United States]] used per year is roughly 94 EJ.
| |
| | |
| ===Zettajoule===
| |
| The zettajoule (ZJ) is equal to one sextillion (10<sup>21</sup>) joules. [[World energy resources and consumption|Annual global energy consumption]] is approximately 0.5 ZJ.
| |
| | |
| ===Yottajoule===
| |
| The yottajoule (YJ) is equal to one septillion (10<sup>24</sup>) joules. This is approximately the amount of energy required to heat the entire volume of [[Water#On Earth|water on Earth]] by 1 °Celsius.
| |
| | |
| ==Conversions==
| |
| {{Main|Conversion of units of energy}}
| |
| 1 joule is equal to:
| |
| * {{val|1|e=7|u=[[erg]]s}} (exactly)
| |
| * {{val|6.24150974|e=18|u=eV}} ([[electronvolt]]s)
| |
| * {{val|0.2390|u=cal}} (thermochemical gram [[calorie]]s or small calories)
| |
| * {{val|2.3901|e=-4|u=kcal}} (thermochemical kilocalories, kilogram calories, large calories or [[food calorie]]s)
| |
| * {{val|9.4782|e=-4|u=BTU}} ([[British thermal unit]])
| |
| * {{val|0.7376|u=ft·lb}} ([[Foot-pound (energy)|foot-pounds]])
| |
| * {{val|23.7|u=ftpdl}} (foot-[[poundal]]s)
| |
| * {{val|2.7778|e=-7|u=[[Kilowatt hour|kilowatt-hour]]}}
| |
| * {{val|2.7778|e=-4|u=watt-hour}}
| |
| * {{val|9.8692|e=-3|u=[[litre]]-[[atmosphere (unit)|atmosphere]]}}
| |
| * {{val|11.1265|u=[[femtogram]]s}} ([[mass-energy]] equivalence)
| |
| * {{val|1|e=-44|u=[[Foe (unit)|foe]]}} (exactly)
| |
| | |
| Units defined exactly in terms of the joule include:
| |
| * 1 thermochemical calorie = 4.184 J<ref name=FAO>[http://www.fao.org/docrep/meeting/009/ae906e/ae906e17.htm 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.</ref>
| |
| * 1 International Table calorie = 4.1868 J<ref name=FAO/>
| |
| * 1 watt hour = 3600 J
| |
| * 1 kilowatt hour = {{val|3.6|e=6|u=J}} (or 3.6 MJ)
| |
| * 1 watt second = {{val|1|u=J}}
| |
| * 1 [[ton TNT]] = 4.184 GJ
| |
| | |
| == See also ==
| |
| | |
| * [[Conversion of units of energy]]
| |
| * [[Orders of magnitude (energy)]]
| |
| * [[Fluence]]
| |
| * [[International System of Units]]
| |
| | |
| == Notes and references ==
| |
| {{Reflist|2}}
| |
| | |
| == External links ==
| |
| * [http://formularium.org/?go=122 Unit conversion from joule]
| |
| | |
| {{SI units}}
| |
| {{Footer energy}}
| |
| | |
| [[Category:SI derived units]]
| |
| [[Category:Units of energy]]
| |