

Standard:  SI derived unit 
Quantity:  Energy 
Symbol:  J 
Named after:  James Prescott Joule 
Expressed in:  1 J = 
SI base units  1 kg·m^{2}/s^{2} 
CGS units  1×10^{7} erg 
The joule (symbol J), named for James Prescott Joule, is the derived unit of energy in the International System of Units. It is the energy exerted by the force of one newton acting to move an object through a distance of one metre. In terms of dimensions:
One joule is defined as the amount of work done by a force of one newton moving an object through a distance of one metre. Other relationships are:
Contents 
This SI unit is named after James Prescott Joule. As with every SI unit whose name is derived from the proper name of a person, the first letter of its symbol is uppercase (J). When an SI unit is spelled out in English, it should always begin with a lowercase letter (joule), except where any word would be capitalized, such as at the beginning of a sentence or in capitalized material such as a title. Note that "degree Celsius" conforms to this rule because the "d" is lowercase.—Based on The International System of Units, section 5.2.
While it is dimensionally correct to express joules as newton metres or N·m, such use is discouraged^{[1]} by the SI authority to avoid confusion with torque. Torque and energy are fundamentally different physical quantities. For example, adding 1 N·m of torque to 1 N·m of energy gives a dimensionally consistent result of 2 N·m, but this quantity is physically meaningless.
One joule in everyday life is approximately:

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.^{[3]}
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 TeV) per particle.
The millijoule (mJ) is equal to one thousandth of one joule.
The kilojoule (kJ) is equal to one thousand joules. Food labels in some countries express food energy in kilojoules. One kilojoule is about the amount of solar radiation received by one square metre of the Earth in one second.^{[4]}
The megajoule (MJ) is equal to one million joules, or approximately the kinetic energy of a oneton vehicle moving at 160 km/h (100 mph).
The gigajoule (GJ) is equal to one billion joules. Six gigajoules is about the amount of chemical energy in a barrel of oil.^{[5]}
The terajoule (TJ) is equal to one trillion joules. About 60 terajoules were released by the bomb that exploded over Hiroshima.^{[6]}
1 joule is equal to:
Units defined exactly in terms of the joule include:

One joule is the work done, or energy expended, by a force of one newton moving an object one metre along the direction of the force. This quantity is also denoted as a Newtonmeter with the symbol N·m. Note that torque also has the same units as work, but the quantities are not identical. In elementary units:
Joule, n., no plural
A joule is a unit in the SI system. That means that scientists use it. It measures the work being done. It is named after James Prescott Joule.
A joule equals one newton multiplied by a meter (1J = 1N × 1m). It is related to the watt (a unit of power): one watt equals one joule per second.
krc:Джоуль
