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Joule heating (also known as resistive, resistance, or Ohmic heating) is the process by which the passage of an electric current through a conductor produces heat.. Joule's first law (also just Joule's law), also known in countries of the former USSR as the Joule–Lenz law, [1] states that the power of heating generated by an electrical conductor equals the product of its resistance and the ...
Between 1840 and 1843, Joule carefully studied the heat produced by an electric current. From this study, he developed Joule's laws of heating, the first of which is commonly referred to as the Joule effect. Joule's first law expresses the relationship between heat generated in a conductor and current flow, resistance, and time. [1]
This was near the time of the 1842–1845 work of James Prescott Joule, measuring the mechanical equivalent of heat. In 1845, Joule published a paper entitled The Mechanical Equivalent of Heat, in which he specified a numerical value for the amount of mechanical work required to "produce a unit of heat", based on heat production by friction in ...
According to the second law, in a reversible heat transfer, an element of heat transferred, , is the product of the temperature (), both of the system and of the sources or destination of the heat, with the increment of the system's conjugate variable, its entropy (): [1]
The joule is named after James Prescott Joule. As with every SI unit named for a person, its symbol starts with an upper case letter (J), but when written in full, it follows the rules for capitalisation of a common noun; i.e., joule becomes capitalised at the beginning of a sentence and in titles but is otherwise in lower case. [7]
James Joule was born in 1818, the son of Benjamin Joule (1784–1858), a wealthy brewer, and his wife, Alice Prescott, on New Bailey Street in Salford. [3] Joule was tutored as a young man by the famous scientist John Dalton and was strongly influenced by chemist William Henry and Manchester engineers Peter Ewart and Eaton Hodgkinson.
Its published results did much to bring about general acceptance of Joule's work and the kinetic theory. However, in 1848, von Mayer had first had sight of Joule's papers and wrote to the French Académie des Sciences to assert priority. His letter was published in the Comptes Rendus and Joule was quick to react. Thomson's close relationship ...
The law was actually the last of the laws to be formulated. First law of thermodynamics d U = δ Q − δ W {\displaystyle dU=\delta Q-\delta W} where d U {\displaystyle dU} is the infinitesimal increase in internal energy of the system, δ Q {\displaystyle \delta Q} is the infinitesimal heat flow into the system, and δ W {\displaystyle \delta ...