- Units of energy
Because

energy is defined via work, theSI unit for**energy**is the same as the unit of work – thejoule (J), named in honour ofJames Prescott Joule and his experiments on themechanical equivalent of heat . In slightly more fundamental terms, 1 joule is equal to 1newton -metre and, in terms ofSI base unit s:$1\; mathrm\{J\}\; =\; 1\; mathrm\{kg\}\; left(\; frac\{mathrm\{m\{mathrm\{s\; ight\; )\; ^\; 2\; =\; 1\; frac\{mathrm\{kg\}\; cdot\; mathrm\{m\}^2\}\{mathrm\{s\}^2\}$

An energy unit that is used in

atomic physics ,particle physics andhigh energy physics is theelectronvolt (eV). One eV is equivalent to 1.60217653×10^{−19}J. Inspectroscopy the unit cm^{-1}= 0.0001239 eV is used to represent energy since energy is inversely proportional to wavelength from the equation $E\; =\; h\; u\; =\; h\; c/lambda$.In discussions of energy production and consumption, the units

barrel of oil equivalent andton of oil equivalent are often used.When discussing amounts of energy released in

explosion s orbolide impact event s, theTNT equivalent unit is often used. 1 ton of TNT equivalent is equal to 4.2 × 10^{9}joules. Therefore, 1 kT TNT is 4.2 × 10^{12}joules, and 1 MT TNT is 4.2 × 10^{15}joules.Note that

torque , the "rotational force" or "angular force" which causes a change in rotational motion is typically expressed in newton-metres. This is not a simple coincidence: a torque of 1 newton-metre applied on 1 radian requires exactly 1 newton-metre = 1 joule of energy.**Other units of energy**In

cgs units, oneerg is 1 g cm^{2}s^{−2}, equal to 1.0×10^{−7}J.The imperial/U.S. units for both energy and work include the

foot-pound force (1.3558 J), theBritish thermal unit (Btu) which has various values in the region of 1055 J, and thehorsepower -hour (2.6845 MJ).The energy unit used for everyday

electricity , particularly for utility bills, is thekilowatt-hour (kWh), and one kWh is equivalent to 3.6×10^{6}J (3600 kJ or 3.6 MJ). Electricity usage is often given in units of kilowatt-hours per year (kWh/yr). This is actually a measurement of average power consumption, i.e., the average rate at which energy is transferred.The

calorie equals the amount ofthermal energy necessary to raise thetemperature of onegram ofwater by 1Celsius degree, at apressure of 1 atm. For thermochemistry a calorie of 4.184 J is used, but other calories have also been defined, such as the International Steam Table calorie of 4.1868 J.Food energy is measured in large calories or kilocalories, often simply written capitalized as "Calories" (= 10^{3}calories).In physics and chemistry, it is still common to measure energy on the atomic scale in the non-SI, but convenient, units

electronvolt s (eV). TheHartree (theatomic unit of energy) is commonly used in calculations. HistoricallyRydberg units have been used.In

spectroscopy and related fields it is common to measure energy levels in units of reciprocal centimetres. These units (cm^{-1}) are strictly speaking not energy units but units proportional to energies, with*hc*being the proportionality constant.**Conversion of units**For conversion of units of energy, see

Conversion of units#Energy, work, or heat .**External links*** [

*http://www.pneumofore.com/support/tools Unit Converter Tool also for Energy*]

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