Contents 1 Usage 2 Confusion with newton metre 3 Practical examples 4 Multiples 4.1 Zeptojoule 4.2 Picojoule 4.3 Nanojoule 4.4 Microjoule 4.5 Millijoule 4.6 Kilojoule 4.7 Megajoule 4.8 Gigajoule 4.9 Terajoule 4.10 Petajoule 4.11 Exajoule 4.12 Zettajoule 4.13 Yottajoule 5 Conversions 6 See also 7 Notes and references

Usage 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.

Confusion with newton metre Main article: newton metre In mechanics, the concept of force (in some direction) has a close analog in the concept of torque (about some angle): Linear Angular force torque mass moment of inertia distance angle A result of this similarity is that the SI unit for torque is the newton metre, which works out algebraically to have the same dimensions as the joule. But they 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 it is simply the newton metre (N⋅m) – a compound name derived from its constituent parts.[5] The use of newton metres for torque and joules for energy is helpful to avoid misunderstandings and miscommunications.[5] The distinction may be seen also in the fact that energy is a scalar – the dot product of a vector force and a vector displacement. By contrast, torque is a vector – the cross product of a distance vector and a force vector. Torque and energy are related to one another by the equation E = τ θ   , {\displaystyle E=\tau \theta \ ,} where E is energy, τ is (the vector magnitude of) torque, and θ is the angle swept (in radians). Since radians are dimensionless, it follows that torque and energy have the same dimensions.

Practical examples One joule in everyday life represents approximately: The energy required to lift a medium-size tomato (100 g) 1 m vertically from the surface of the Earth.[6] 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 distance of 1 m. The heat required to raise the temperature of 1 g of water by 0.24 °C.[7] The typical energy released as heat by a person at rest every 1/60 s (approximately 17 ms).[8] 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).[9] 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 W LED for 1 s. Since the joule is also a watt-second and the common unit for electricity sales to homes is the kW⋅h (kilowatt-hour), a kW⋅h is thus 1000 W × 3600 s = 3.6 MJ (megajoules).

Conversions Main article: Conversion of units of energy 1 joule is equal to: 7000100000000000000♠1×107 erg (exactly) 7000100000001488094♠6.24150974×1018 eV 6999999976000000000♠0.2390 cal (gram calories) 6999999976000000000♠2.390×10−4 kcal (food calories) 7000100000303823028♠9.4782×10−4 BTU 6999737600000000000♠0.7376 ft⋅lb (foot-pound) 6999998720609223173♠23.7 ft⋅pdl (foot-poundal) 6993277780000000000♠2.7778×10−7 kW⋅h (Kilowatt hour) 6996277780000000000♠2.7778×10−4 W⋅h (Watt hour) 6999999996690000000♠9.8692×10−3 l⋅atm (litre-atmosphere) 6983111265000000000♠11.1265×10−15 g (by way of mass-energy equivalence) 7000100000000000000♠1×10−44 foe (exactly) Units defined exactly in terms of the joule include: 1 thermochemical calorie = 4.184 J[18] 1 International Table calorie = 4.1868 J[19] 1 W⋅h = 3600 J (or 3.6 kJ) 1 kW⋅h = 7006360000000000000♠3.6×106 J (or 3.6 MJ) 1 W⋅s = 7000100000000000000♠1 J 1 ton TNT = 7009418400000000000♠4.184 GJ

See also Look up joule in Wiktionary, the free dictionary. Conversion of units of energy Orders of magnitude (energy) Fluence International System of Units Watt second