(December 24, 1818 – October 11, 1889)
Through his brewing experiences and obsessions with thermal energy, James Joule was able to make significant discoveries, which ensured that his name Joule was designated the S.I. unit of energy. By demonstrating the link between heat and mechanical work, he inadvertently plotted the Law of Energy Conservation which culminated in the First Law of Thermodynamics. He then used his understanding of heat to rebut the Caloric Theory (which vaguely claimed that heat is an aggregate of self-repellent fluids). Joule studied under Britain’s leading thermal researchers of his era including: John Dalton, William Henry, Eaton Hodgkinson and Peter Ewart. After assessing both the Dalton’s Law of Partial Pressures and Henry’s Law Constant, (amongst others); he sought to correlate heat energy with the Kinetic Theory. He later collaborated with William Thomson Kelvin during Kelvin’s work on his absolute temperature scale. He was also interested in electricity, and how it could output heat. This saw him experimenting with batteries in 1841: evaluating how the current passed through conductors relate to the heat they generated. He subsequently confirmed that the power of heating generated by a conductor is proportional to the product of its resistance and the square of the current. This inference is known now as Joule-Lenz Law: in honor of himself and Heinrich Lenz (who discovered it independently in 1842). Again in 1842, while researching with nickels, Joule discovered magnetostriction (the ability of ferromagnetic materials to alter their dimensions when exposed to magnetic fields). Dedicated to him is the 96-kilometer-wide Joule lunar crater.