THIS IS MY LIFE

JOULE, James Prescott (1818-89), British physicist, born in Salford, Lancashire, England. One of the outstand ing physicists of his day, Joule is best known for his research in electricity and thermodynamics. In the course of his investigations of the heat emitted in an electrical circuit, he formulated the law, now known as Joule's law, of electric heating, which states that the amount of heat produced each second in a conductor by a current of electricity is proportional to the resistance of the conductor and to the square of the current. Joule experimentally verified the law of conservation of energy in his study of the transfer of mechanical energy into heat energy. Using many independent methods, Joule determined the numerical relation between heat and mechanical energy, or the mechanical equivalent of heat. The unit of energy called the joule is named after him; it is equal to 1 watt-second, or 10 million ergs, or about 0.000948 British thermal unit. Together with the physicist William Thomson (later Baron Kelvin), Joule found that the temperature of a gas falls when it expands without doing any work. This principle, which became known as the Joule-Thomson effect, underlies the operation of common refrigeration and air conditioning systems.