# Joule's law

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## Joule's law:

see thermoelectricity**thermoelectricity,**

direct conversion of heat into electric energy, or vice versa. The term is generally restricted to the irreversible conversion of electricity into heat described by the English physicist James P.

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## Joule's law

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* = *RI*^{2}, 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.

## Joule’s Law

(in Russian, Joule-Lents [Lenz] law), a law that defines the amount of heat *Q* liberated in a conductor when an electric current passes through it; *Q* is proportional to the conductor’s resistance *R* and to the square of the current *I* in the circuit and the time *t* for which the current flows: *Q = aI ^{2}Rt*. Here

*a*is a proportionality coefficient that de-pends on the units of measurement used; if

*I*is in amperes,

*R*in ohms, and

*t*in seconds, then

*fora =*0.239,

*Q*is in calories, but if

*a=*1,

*Q*is in joules. Calculations for electric lighting arrangements and electric heating devices are based on Joule’s law.

The law was established in 1841 by the English physicist J. Joule and was discovered independently in 1842 by the Russian scientist E. Kh. Lents (H. F. E. Lenz).

## Joule's law

[′jülz ‚lȯ]## Joule's law

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* = *RI*^{2}, 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. *See* Electric heating