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[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] Physical quantities measured in J·mol −1 usually describe quantities of energy transferred during phase transformations or chemical ...
Energy density is thus commonly expressed in metric units of cal/g, kcal/g, J/g, kJ/g, MJ/kg, cal/mL, kcal/mL, J/mL, or kJ/mL. Energy density measures the energy released when the food is metabolized by a healthy organism when it ingests the food (see food energy for calculation).
One square metre of the Earth receives about 1.4 kilojoules of solar radiation every second in full daylight. [19] A human in a sprint has approximately 3 kJ of kinetic energy, [20] while a cheetah in a 122 km/h (76 mph) sprint has approximately 20 kJ. [21] One watt-hour, of electricity or any other form of energy, is 3.6 kJ. megajoule
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 daily light integral (DLI) is the number of photosynthetically active photons (photons in the PAR range) accumulated in a square meter over the course of a day. It is a function of photosynthetic light intensity and duration (day length) and is usually expressed as moles of light (mol photons) per square meter (m −2) per day (d −1), or: mol·m −2 ·d −1.
The British imperial units and U.S. customary units for both energy and work include the foot-pound force (1.3558 J), the British thermal unit (BTU) which has various values in the region of 1055 J, the horsepower-hour (2.6845 MJ), and the gasoline gallon equivalent (about 120 MJ).
The formula defines the energy E of a particle in its rest frame as the product of mass (m) with the speed of light squared (c 2). Because the speed of light is a large number in everyday units (approximately 300 000 km/s or 186 000 mi/s), the formula implies that a small amount of mass corresponds to an enormous amount of energy.
Energy conversion efficiency (η) is the ratio between the useful output of an energy conversion machine and the input, in energy terms. The input, as well as the useful output may be chemical, electric power, mechanical work, light (radiation), or heat. The resulting value, η (eta), ranges between 0 and 1. [1] [2] [3]