Mechanical equivalent of heat

In the history of science, the mechanical equivalent of heat was a concept that played an important part in the development and acceptance of the conservation of energy and the establishment of the science of thermodynamics in the 19th century.

Related Topics:
History of science - Concept - Conservation of energy - Thermodynamics - 19th century

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The idea was proposed by Julius Robert von Mayer (1842) and independently by James Prescott Joule (1843). Similar work was carried out by Ludwig A. Colding (1840-1843). Joule contended that motion and heat were mutually interchangeable and that in every case, a given amount of work would generate the same amount of heat. Joule experimented on the amount of mechanical work needed to raise the temperature of a pound of water by one degree Fahrenheit and found a consistent value of 772.24 foot pound force (4.1550 J·cal-1).

Related Topics:
Julius Robert von Mayer - 1842 - James Prescott Joule - 1843 - Ludwig A. Colding - 1840 - Motion - Heat - Work - Temperature - Pound - Water - Fahrenheit - Foot pound force - J - Cal

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Though a standardised value of 4.1860 J·cal-1 was established in the early 20th century, in the 1920s, it was ultimately realised that the constant is simply the specific heat of water, a quantity that varies with temperature between the values of 4.17 and 4.22 J·g-1·°C-1.

Related Topics:
20th century - 1920s - Specific heat - G - °C

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The change in unit has been the result of the demise of the calorie as a unit in physics and chemistry.

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