Most of us who know of James Joule know of him because we have heard of Joule’s law, his paddle experiment and/or we know that energy is measured in Joules in his honor. But who was Joule and how and why did he make his discoveries and what does it have to do with his friendship with a young scientist named William Thomson later knighted Lord Kelvin?
James Prescott Joule was born on Christmas Eve in 1818, and was the grandson of William Joule who had founded a popular brewery called Joule’s Brewery which James’ father ran after his grandfather’s death. James, who was prevented from going to school due to a “weak” spine and his best-friend and older brother John, were tutored together and enjoyed rowing, riding horses and playing electric tricks on each other even recreating Benjamin Franklin’s electric kite experiment for fun (there is no mention of what James’ younger sisters did). In 1834, the Joule brothers were tutored in Chemistry by the now famous Chemist John Dalton, who popularized the idea of atoms in chemistry, although he spent most of his time tutoring them in Math which Dalton felt they were lacking. By the time James Joule was 18 years old, Joule worked at the brewery seven days a week from 9 am till 6 pm, but still found time to tinker with experiments in a spare room in his father’s house.
It was around this time that Joule learned about electric motors and was inspired. See, a former shoemaker and soldier who had invented the electromagnet in 1826 named William Sturgeon had trouble with getting published so he started a magazine where he promised that, “Every description of new experiment or instrument in Electricity, Magnetism, Electro-Magnetism, Magnetic Electricity, and Electro-Chemistry, will find a place in this work.” In his first publication, in October, 1836, Sturgeon published a description of a motor he had made with electromagnets which he claimed could be used “for drawing water, wagons and carriages on a railway… [and] upon the same scale as we see pieces of machinery put into motion by the large models of steam engines.” In retrospect, it is clear that Sturgeon was exaggerating and his motor could barely spin let alone being on the same scale as steam engines, but it motivated Joule (and much of England) to try to make their own electric motor. Secondly, the following year, Sturgeon published the account from a Russian/German man named Moritz Jacobi who had designed a better motor than Sturgeon (and published it first as well), which could produce 15 watts of power. Jacobi not only created the world’s most powerful motor, he also wrote a paper that described Ohm’s law in a simple and convincing way which is how Joule learned of it.
Joule then used these ideas to create his own motor and published a description of it, at the age of 19, in Sturgeon’s paper in February of 1838. Joule was quickly convinced that electric motors were going to be powerful soon, writing, “I can scarcely doubt that electro-magnetism will eventually be substituted for steam in propelling machinery.” Joule designed system after system but he felt frustrated that he couldn’t get his machine to have much power. To improve the motor, created a new galvanometer (or machine to measure the current). Joule then decided to make precise experiments on electromagnetic attraction as he needed a galvanometer with readings, “which could be depended on.” It was these studies that led Joule to realize that he could use Faraday’s laws of electrolysis to quantitatively measure how much electricity was produced by how much hydrogen was decomposed, so his, or anyone’s, galvanometer could be calibrated, as at this time they had no standard units for current. With this more accurate measurement device, Joule decided to systematically study how much heat that electricity could produce and by the end of 1840, had determined that the heat produced by a wire, “is proportional to the resistance of the conductor multiplied by the square of the electric intensity.” This equation, known as Joule’s Law, is still commonly used today!
In 1841 and 42, James Joule made more experiments on the relation between electricity and heat and realized that the amount of heat made by the current was proportional to the chemical reactions inside the battery. Joule then became convinced that heat was not an indestructible “calorific” as most thought at the time, but instead something that could be created by work, or, in reverse, heat could be used to do work. By August of 1843, Joule was trying to convince anyone and everyone that, “wherever mechanical force is expended, an exact equivalent of heat is always obtained.” As Joule was discussing how heat transfers, this was eventually called thermodynamics, and Joule’s statement is a form of the first law of thermodynamics, that heat is a form of energy and energy is conserved. However, Joule’s measurements were so accurate that scientists doubted him and his theories that heat was just motion of atoms was ridiculed and, as he was just a beer brewer, he was mostly ignored.
Undeterred, Joule continued to travel around and give talks about conservation of energy to various uninterested parties. By June of 1845, Joule created his most famous experiment, the paddle wheel to demonstrate “the mechanical equivalent of heat”. In this experiment, he dropped a weight from a height which turns a paddle and then measured the temperature change of the water. In this way, he found that 817 pounds at a height of 1 foot was equivalent to raising the temperature of 1 kg of water by 1 degree Fahrenheit “until more accurate experiments shall have been made” (side note: Joule improved his experiment in 1849 and got a weight of 772.692 pounds, which corresponds with 4,160 J/Cal in modern units: the currently accepted value is 4,150 J/Cal)
Anyway, on June 23, 1847, Joule gave a talk at the British Association for the Advancement of Science where a 23-year-old Scottish scientist named William Thomson heard him. Years later, Thomson recalled that when he heard Joule talk, he, “felt strongly impelled to rise and say that it must be wrong,” because it opposed the writings of a French scientist named Sadi Carnot who wrote about how heat was indestructible. However, as Thomson listened to Joule, he realized that at least some of what Joule said was, “a great truth and a great discovery.” They talked afterwards and it, according to Thomson, “quickly ripened into a life-long friendship”. This friendship became a family affair when, a week after this talk, James Joule married a woman named Amelia Grimes and William Thomson accidentally bumped into them conducting science experiments on their honeymoon, which he was invited to join (the experiment not the honeymoon).
This was an important friendship because the next year, 1848, Thomson became internationally famous when he published his theory of how to use Sadi Carnot’s theories to derive absolute zero temperature (which he derived to be -273 degrees Celsius) By the way, Thomson was knighted and made the Baron Kelvin in 1892, and the temperature scale is named after him. In this landmark paper, Thomson used the idea of an indestructible heat which Thomson said was a view “nearly universally held” except by Mr. Joule who had made, according to Thomson, some, “very remarkable discoveries on the subject.”
In Germany, a 27-year-old high school teacher named Rudolf Clausius read Thomson’s work and then Joule’s work and was inspired by everything except the idea that heat was indestructible. Instead, Clausius felt that heat is a form of energy and it is the energy that is conserved partially because of what he called the “careful experiments of Joule”. Clausius was not the first to promote the idea of energy conservation, but he was the first to state that energy conservation does not require one “to discard Carnot’s theory entirely” but merely the idea that “no heat is lost”.
Thomson really hated Clausius’s paper and soon Thomson and Clausius published articles debating each other’s ideas. It is not clear how Joule felt about Clausius, but, as he and Thomson were such close friends, it seems likely that he also disliked Clausius. Despite this, Thomson changed his mind about the “calorific” and then published a series of five papers “On the Dynamical Theory of Heat” between 1851 and 1855 where he lay out new mathematics and theories on the conservation of energy which (along with Clausius’s papers) laid the foundations of the laws of thermodynamics. In addition, James Joule and William Thomson started to collaborate on papers between 1852 and 1856 did a lot to increase the acceptance of not only the idea of energy conservation but also of the existence of atoms.
At first, this was a happy time in Joule’s life, his ideas were starting to be accepted by some of the biggest scientists in the world and his marriage to Amelia was strong with the birth of two children, Benjamin in 1850 and Alice in 1852. All of that changed in June of 1854 when Amelia had a difficult time giving birth to their third child, who died 20 days later. By July 6th, Joule wrote Thomson about the tragic news and that he was “very much alarmed about my dear wife” who was not recovering well. She died 2 months later.
Joule was devastated and quit his scientific work, and moved with his children back to his father’s house. With the love and support of his family, Joule started to regain his interest in science and in 1855, Thomson convinced Joule to continue his studies in electrodynamics as well as fluids, but he was never the same. Still, Joule began to receive awards for his work and was given an honorary doctorate. In 1863, was added to the British Association’s committee on electrical standards, where he helped Thomson (and others) to name and standardize the units of charge, current, voltage, and resistance, and, in 1867, the report stated that, “the most important experiments have been those conducted by Dr. Joule.” In 1870, Joule received the Royal Societies top honor, the Copley Medal in 1870, “for his experimental researches on the dynamical theory of heat”. Joule then retired from scientific work and in 1878, the Queen of England awarded him a pension for his work. In 1882, the President of the British Association for the Advancement of Science suggested that energy be measured in Joules in honor of James Joule, which we continue to do to this day. James Joule died seven years later at the age of 70 in 1889 and his grave has the number 772.55 for his final measurement for the weight in pounds to heat 1 pound of water by 1 degree Fahrenheit.
That is a little background on James Joule. It was interesting for me to look at the 1863 Committee on Electrical Standards, as there is not only William Thomson and James Joule but also James Clerk Maxwell (who I have a video about), Charles Wheatstone (who I just finished a video about), and Balfour Stewart (who I mention in my video about the astronomer Norman Lockyer). In addition, the committee had Carl Siemens and Cromwell Varley, whose brothers (Ernst Siemens and Samuel Varley) both claimed that they were both the first to independently invent generators that used electromagnets instead of permanent magnets and use self-excitation (divert some of the electricity to power the electromagnet). However, Cromwell Varley worked for Charles Wheatstone who also claimed that he had invented the generator and Cromwell backed his boss instead of his brother. I go over a bit of that controversy in my video about the history of the Generator. However, that video has a big mistake. In it, I claim that Nikola Tesla invented the three-phase three wire generator and electrical distribution system, but he didn’t. How three phase works and why it was invented and why Tesla often falsely gets the credit is next time on the lightning tamers.
 Reynolds, O Memoir of James Prescott Joule (1892) p. 25-6
 Cardwell, D James Joule (1989) p. 30
 Sturgeon, W “Prospectus” The Annals of Electricity, vol. 1 (1836) p. ii
 Sturgeon, W “Description of an Electro-magnetic Engine” The Annals of Electricity, vol. 1(October, 1836) p. 78
 Joule, J “Description of an electro-magnetic engine“ (Jan, 1838) Annals of Electricity, vol. 2 p. 122
 Joule, J “Investigations in Magnetism and Electro-magnetism” (May 1839) Annals of Electricity, vol. 4 p. 135
 ibid p. 131
 Joule, J “On the Heat Evolved by Metallic Conductors of Electricity” (Aug 1841) The Scientific Papers of James Prescott Joule Vol. 1 (1884) p. 61
 Ibid p. 65
 Joule, J “On the Calorific Effects of Magneto-Electricity” (Aug 1843) The Scientific Papers of James Prescott Joule Vol. 1 (1884) p. 157
 William Thomson to J.T. Bottomley in 1882 found in Reynolds, O Memoir of James Prescott Joule (1892) p. 108
 Thomson, W “On an Absolute Thermometric Scale…” (June 5, 1848) Proceedings – Cambridge Philosophical Society vol. 1 & 2 p. 68
 Clausius, R “On the Moving Force of Heat..” (Translated in English July, 1851) The London, Edinburgh and Dublin Philosophical Magazine Vol. 2 (1851)p. 2 & 4
 Clausius, R “First Memoir” (1850) The Mechanical Theory of Heat (1867) p. 17
 Clausius, R “First Memoir” (1850) The Mechanical Theory of Heat (1867) p. 17
 “Report of the Committee” Report of the British Association for the Advancement of Science (1867) p. 474
 Siemens, C Report of the Fifty-Second Meeting of the British Association for the Advancement of Science (1883)