James Prescott Joules (Joule James Prescott)

(1818-1889)
Born in Salford, near Manchester on Dec. 24, 1818. He received education at home. For several years he taught mathematics, physics, chemistry beginnings of the famous physicist and chemist Dzh.Dalton, under the influence of which Joule had in 19 years began experimental studies. In 1838 in the journal Annals of electricity '(' Annals of Electricity ') published his article describing the electromagnetic motor, in 1840 he discovered the effect of magnetic saturation, in 1842 - the phenomenon of magnetostriction. Influenced by the work of Faraday turned to the study of thermal effects of current, which resulted in the discovery of the law, is now called Joule - Lenz (1842 regardless of this law was discovered by Russian physicist Erwin H. Lenz). According to this law, the amount of heat released in the conductor is proportional to the resistance of the conductor and the square of the amperage. In 1843 Joule took up a new challenge: proving the existence of quantitative relations between the 'forces' of different nature, resulting in heat release. His first experiments consisted in measuring the amount of heat released in the vessel with water, which under the action of the sinking of cargo moved the electromagnet, and the vessel was placed in a magnetic field. In these experiments, he first determined the mechanical equivalent of heat (4.5 J / cal modern units), and in subsequent years investigated the thermal effects due to bursting of the liquid through the narrow openings (1844), compression of gas (1845), etc.. All these experiments led to the discovery of the Joule energy conservation law. Subsequently, his name was called the unit of measurement for all types of energy - mechanical, thermal, electrical, radiant, etc.. In 1847, Joule became acquainted with W. Thomson, and studied with him the behavior of gases under different conditions. The result of this collaboration was the discovery of the effects of cooling gas at a slow adiabatic flow it through a porous membrane (the effect of Joule - Thomson). This effect is used for liquefaction of gases. In addition, Joule has constructed a thermodynamic temperature scale, calculated the heat capacity of certain gases, calculated the velocity of the gas molecules and established its dependence on temperature. Among the awards and honors, which was awarded a scientist - the Gold Medal of the Royal Society (1852), the Copley medal (1866), the Albert Medal (1880). In 1872 and 1877 Joule was elected president of the British Association for the Advancement of Science. Joule died in Salem on Oct. 11, 1889.