Joule, James Prescott
The Englishman James Prescott Joule (1818 - 1889), son to a brewer, was a physicist.
He studied the nature of heat. He formulated the law of conservation of energy, which in turn led to the development of the first law of thermodynamics. He estimated the mechanical equivalent of heat as 4.1868 joules per calorie.
He found that the power (P) of heating generated by an electrical conductor equals the product of its resistance (R) and the square of the current (I), which is also called Joule's first law:
power (P) = resistance (R) × [ current (I) ]2
He worked with Lord Kelvin to develop an absolute temperature scale known as Kelvin scale.
He lent his name to to the joule, the unit of energy.
See also
Last modified:10 January 2026 2.53 p.m.