Article
Article
Joule's law
Article By:
Hoxton, Lewellyn G. Formerly, Physics Department, University of Virginia, Charlottesville, Virginia.
Stewart, John W. Department of Physics, University of Virginia, Charlottesville, Virginia.
Last reviewed:January 2020
DOI:https://doi.org/10.1036/1097-8542.360400
A quantitative relationship between the quantity of heat produced in a conductor and an electric current flowing through it. As experimentally determined and announced by J. P. Joule, the law states that when a current of voltaic electricity is propagated along a metallic conductor, the heat evolved in a given time is proportional to the resistance of the conductor multiplied by the square of the electric intensity. Today the law would be stated as H = RI2, where H is rate of evolution of heat in watts, the unit of heat being the joule; R is resistance in ohms; and I is current in amperes. This statement is more general than the one sometimes given that specifies that R be independent of I. Also, it is now known that the application of the law is not limited to metallic conductors.
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