James Prescott Joule

James Prescott Joule (1818 to 1889) was an English physicist and brewery manager from Salford whose measurements tied heat to mechanical work. Around 1840 he asked whether the brewery steam engines could be replaced by electric motors, found that a pound of coal burned in a steam engine did more work than a pound of zinc consumed in a battery, and went on to ask how much work could be drawn from a given source at all. His experiments, including the paddle wheel apparatus reported in 1845, gave a mechanical equivalent of heat and supported the conservation of energy and the first law of thermodynamics. He also stated Joule heating, the relation between current, resistance and heat, and worked with Lord Kelvin on an absolute temperature scale. The joule, the SI unit of energy, is named for him.