The joule (symbol J, also called newton metre, or coulomb volt) is the SI unit of energy and work. The unit is pronounced to rhyme with "tool", and is named in honour of the physicist James Prescott Joule (1818-1889).
1 joule = 1 N · 1 m = 1 newton · 1 metre = 1 kg · 1 m2 · 1 s−2
One joule is the work required to exert a force of one newton for a distance of one metre, so the same quantity may be referred to as a newton metre or newton-metre (also with meter spelling), symbol N·m or N m. However, to avoid confusion the newton metre is usually used as a measure of torque, not energy.
Another way of visualizing the joule is the work required to lift a mass of about 102 g (e.g. a small apple) for one metre under the earth's gravity.
One joule is also the work required to move an electric charge of 1 coulomb through an electrical potential difference of 1 volt.
One joule is also the work done to produce power of one watt for one second, such as when somebody takes one second to lift the small apple mentioned above through one metre under the earth's gravity.
The joule is a derived unit defined as the work done or energy required, to exert a force of one newton for a distance of one metre, so the same quantity may be referred to as a newtonmetre or newton-metre with the symbol N·m.
Its value was found by James Prescott Joule in experiments that showed the mechanicalenergyJoule's equivalent, and represented by the symbol J. The term was first introduced by Dr. Mayer of Heilbronn.
The SI unit of work, the joule, is named after him, and is pronounced to rhyme with "tool." He worked with Lord Kelvin to develop the absolute scale of temperature, made observations on magnetostriction, and found the relationship between the flow of current through a resistance and the heat dissipated, now called Joule's law.
Joule was influenced by the thinking of Franz Aepinus and tried to explain the phenomena of electricity and magnetism in terms of atoms surrounded by a "calorific ether in a state of vibration".
Joule was a pupil of Dalton and it is no surprise that he had learned a firm belief in the atomic theory, even though there were many scientists of his time who were still skeptical.
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