Who is James Prescott Joule?June 25, 2021
He discovered the relationship of heat to mechanical work. This discovery led to the theory of conservation of energy and from there the first law of thermodynamics. The unit of work in the SI system, the joule, is named after him. He developed the absolute temperature scale with Lord Kelvin. He found that an electric current passing through a resistor emits heat (Joule’s law).
Mechanical equivalent of heat
Q = c Δt m = 4.18 F Δx = 4.18 W
Q = Heat (cal)
c = core temperature (cal/g degrees centigrade)
Δt = temperature change (degrees centigrade)
m = mass (g)
F = conservative force doing work (Newtons)
Δx = displacement (meters)
W = physical work (joules)
Joule, as a result of his experiments, as the mechanical equivalent of heat; found that it takes 838 ft·lbf of work to raise the temperature of one pound of water by one degree Fahrenheit. Joule announced these results at the “British Association for the Advancement of Science” meeting held in 1843, but did not receive the attention he expected.