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Energy; system unit code (alternative) symbol or abbrev. notes sample default conversion combinations SI: yottajoule: YJ YJ 1.0 YJ (2.8 × 10 17 kWh) zettajoule: ZJ ZJ 1.0 ZJ (2.8 × 10 14 kWh)
The kilowatt-hour is a composite unit of energy equal to one kilowatt (kW) sustained for (multiplied by) one hour. The International System of Units (SI) unit of energy meanwhile is the joule (symbol J). Because a watt is by definition one joule per second, and because there are 3,600 seconds in an hour, one kWh equals 3,600 kilojoules or 3.6 ...
One square metre of the Earth receives about 1.4 kilojoules of solar radiation every second in full daylight. [20] A human in a sprint has approximately 3 kJ of kinetic energy, [21] while a cheetah in a 122 km/h (76 mph) sprint has approximately 20 kJ. [22] One watt-hour, of electricity or any other form of energy, is 3.6 kJ. megajoule
In general, proteins have lower energy densities (≈16 kJ/g) than carbohydrates (≈17 kJ/g), whereas fats provide much higher energy densities (≈38 kJ/g), [8] 2 + 1 ⁄ 4 times as much energy. Fats contain more carbon-carbon and carbon-hydrogen bonds than carbohydrates or proteins, yielding higher energy density. [ 9 ]
1 kJ/mol, converted to energy per molecule [9] 2.1×10 −21 J Thermal energy in each degree of freedom of a molecule at 25 °C (kT/2) (0.01 eV) [10] 2.856×10 −21 J By Landauer's principle, the minimum amount of energy required at 25 °C to change one bit of information 3–7×10 −21 J
The watt, kilogram, joule, and the second are part of the International System of Units (SI). The hour is not, though it is accepted for use with the SI.Since a watt equals one joule per second and because one hour equals 3600 seconds, one watt-hour per kilogram can be expressed in SI units as 3600 joules per kilogram.
It is also an SI derived unit of molar thermodynamic energy defined as the energy equal to one joule in one mole of substance. [1] [2] For example, the Gibbs free energy of a compound in the area of thermochemistry is often quantified in units of kilojoules per mole (symbol: kJ·mol −1 or kJ/mol), with 1 kilojoule = 1000 joules. [3]
The energy content of ethanol is 76,100 BTU/US gal (5.89 kilowatt-hours per litre), compared to 114,100 BTU/US gal (8.83 kWh/L) for gasoline. (see chart above) A flex-fuel vehicle will experience about 76% of the fuel mileage MPG when using E85 (85% ethanol) products as compared to 100% gasoline. Simple calculations of the BTU values of the ...