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Joule's name is common in everyday life as the SI unit of energy found on food packaging. 1 joule = 0.24 calorie.James Prescott Joule (1818-99) was the son of a wealthy Salford brewer. He became interested in science through receiving tuition from John Dalton, famed for his atomic theory. Joule set up a laboratory in the cellar of the family home. He began a series of experiments on the nature of energy and published the findings that became known as Joule's first law in 1840.

His next experiments used a paddlewheel and calorimeter to prove that heat and mechanical work are both forms of energy. At a British Association meeting in 1843, he gave a paper that introduced the physical constant now known as 'J' or Jouleâ??s Equivalent. Previously scientists had believed that heat was a fluid known as 'caloric'. Joule's theory of the 'Mechanical Equivalent of Heat' laid the basis for the first law of thermodynamics.

Joule's name is common in everyday life as the SI unit of energy found on food packaging. 1 joule = 0.24 calorie.