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More than 5000 entries on the history, culture and life of Britain (published in 1993 by Macmillan, now out of print)
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James Joule
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(1818–89) Physicist, born the son of a Lancashire brewer, who was taught science by John *Dalton and then experimented in a laboratory set up for him in his parents' house. In 1840 he announced his first major discovery, known now as Joule's Law (the heat produced by an electric current is proportional to the resistance of the conductor times the square of the current). In 1843, after long and painstaking experiment, he published a figure for the mechanical equivalent of heat; in doing so he incidentally demonstrated the first law of thermodynamics, that a constant amount of energy is required to produce a given quantity of heat and can equally be derived from it.
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By 1849 Joule had refined his figure to 772 ft-lb required to raise 1 lb of water by 1° Fahrenheit (the equivalent British thermal unit in use today is 778 ft-lb). In the 1850s he experimented with William *Thomson on gases; the Joule-Thomson effect describes the drop in temperature caused by an expanding gas and is the principle of household refrigerators. In modern science a joule is the derived SI unit of work or energy.
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