James Prescott Joule. Biography

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James Prescott Joule (1818-1889). Biography of a scientist

Directory / The life of remarkable physicists

James Prescott Joule (1818-1889)
James Prescott Joule

The unit of work and energy is named after him not only in electrical engineering, but also in other fields of science.

Joule was born in the small town of Salford near Manchester (Great Britain) on December 24, 1818. His father was rich (he had a brewery in Manchester), and since little Joule was very sickly, he received his school education at home. Among his home teachers was, for example, John Dalton (remember the term "color blindness"). He not only taught mathematics to Joule, but also taught him the basics of physics and chemistry, introduced him to laboratory equipment. Joule became interested in physical experiments.

Experimenting with the first electric motors, Joule discovered that the power of the motor is proportional to the product of the current and the EMF of the battery from which the motor was powered (and this is now so obvious!). In the period from 1840 to 1847, Joule studied the thermal effect of electric current and found that the amount of heat released in the wire through which the current flows is proportional to the product of the resistance of the conductor and the square of the current strength (now these are school formulas). Working with another famous physicist, William Thomson, Joule found that if a gas is expanded without doing work (adiabatic expansion), then its temperature decreases. This effect has been called the Joule-Thomson effect and is at the heart of modern refrigeration and air conditioning technology.

In his work, Joule established that there is a close relationship between mechanical and thermal energy. He calculated the mechanical equivalent of heat. Joule made a great contribution to thermodynamics, confirming the law of conservation of energy. Joule considered heat as the movement of particles. He calculated the speed of movement of gas molecules and established its dependence on temperature.

The significance of Joule's work was already highly appreciated by his contemporaries. In 1850 Joule was elected a Fellow of the British Royal Society. He was also honorary doctor of many European universities and learned societies. When the international SI system of units was introduced in 1961, the unit of work and energy was rightfully named after him.

James Prescott Joule died on October 11, 1889.

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