James Prescott Joule is credited with the fundamental discovery that opened a new paradigm of the nature of heat, which allowed many new discoveries and inventions. A rather unassuming man in appearance, he had difficulty for a long time in convincing his contemporaries of the importance of his discovery. However, once he received the endorsement of an accepted scientist William Thomson Kelvin, he received nearly immediate acclaim. Though he continued his work throughout his life, all of the discoveries for which he is now famous were accomplished before he was 34 years old. One truly noteworthy condition of Joule's career was that he was self-reliant in his education and his research. He was self-educated and, coming from a wealthy family, he funded his own research. This condition, as respectable as it was, proved to be a great hindrance. The scientific community would not believe that Joule could discover something so important without the support, academically and financially, of an academic institution. Still, he knew that he had the answer to a long-puzzling scientific question and he persevered.
Joule is noted in the history of science as one of the most determined researchers. He even produced research while on his honeymoon. Joule and his bride were visiting Switzerland and Joule took the occasion to measure the temperature of a large waterfall as part of his research. By chance, Kelvin met him on the mountain that day and long after admired his determination. Joule was a great influence on Kelvin and many others for his breakthrough, his methods, and his persistence.
Joule was born in 1818 in Salford, England. He grew up in a well- established wealthy family, which had owned a brewery for generations. As a child, Joule was not very healthy and was educated at home through tutors and his own readings. When he was 16, he went to study for two years with John Dalton. Dalton first stimulated Joule's interested in chemistry and experimentation. After Dalton could no longer teach because of his poor health, Joule built his own laboratory at his family's home. He conducted experiments and began writing research papers when he was 20. In the autumn before he turned 23, Joule presented a paper at the meeting of the Manchester Literary and Philosophical Society. He was well received and was soon elected as a member of the society. He was an active member of the society for many years, culminating in his acceptance of the society presidency in 1860.
Joule never attended college. Instead, he read incessantly on whatever interested him and what did not interest him he avoided. He abhorred some of the topics usually considered part of a liberal college education. Still, he was fascinated with the study of physics, in particular electromagnetic fields. In 1838, he described in a paper what he called an electromagnetic engine. He believed that these engines could replace steam but later had to admit their inefficiency. In 1840, he wrote a paper describing what is now called the Joule effect. His premise was that the amount of heat produced by electrical current is a function of the amount of resistance and the square of the current.
From 1843 through 1878, he regularly attended the meetings of the British Association for Advancement of Science (BAAS). At his first meeting, he presented his seminal theory on the nature of heat. This theory stated that heat is derived from work and that heat and work are interchangeable. He worked to improve this theory and every year returned to the BAAS to present a paper reporting his progress. At the 1845 meeting, he brought a working model demonstrating the work-to-heat principle. This model consisted of water in a container that was agitated very fast by a paddle. The main problem with the conference attendees accepting his theory was that the experiments supporting the theory required highly precise measurements of heat. They did not appreciate that Joule, an amateur, had taken this preciseness into consideration.
After tolerating Joule for five years, the conference administrators requested that he give a summary of his findings and not a full presentation. This was the historic 1847 meeting where Kelvin rose to the defense of Joule's theory. After the short presentation, Kelvin asked so many questions that Joule had to go into his full presentation. Kelvin's fascination with the theory stirred up new interest among the scientists. Kelvin announced to the conference that he found Joule's methods and findings to be well developed and accurate. This was a turning point in Joule's career.
Only days after that turning point, Joule took a turning point in his life. He married Amelia Grimes who apparently was good-natured about his constantly measuring heat. When he saw the high waterfall on his honeymoon, he wanted to test his theory and she willingly helped him. He deduced that the water at the bottom of the fall should be hotter than at the top due to the work of the water running down the fall. As noted above, he met Kelvin again that day. Joule and Kelvin began collaboration from 1853 through 1862. During that time, they established the Joule-Thomson effect.
Joule's heat theory was the cornerstone of his research career. One of the embellishments involved the calculation of the velocity of a gas molecule in 1848. He developed relatively little more in his life but it was enough to eventually lead Kelvin and others to discover the second principle of thermodynamics. After 1862 when he was no longer doing research with Kelvin, Joule revised his theory as an expression of the conservation of energy. He died in 1889 at age 71.
Joule's heat-to-work theory was well founded in his experiments. He had done an exhaustive amount of work to determine that the relationship between heat and work was a constant. He even calculated the amount of work necessary to produce heat. Once his views were "approved" by Kelvin's endorsement, many researchers excitedly investigated his theory. They found that the number Joule used as his work-to-heat constant was too large. To find a more practical unit of measurement, they divided Joule's number by 10,000,000 and named the new unit after him. The measure of heat equivalent to work is now called the joule.
Working with Kelvin, Joule investigated different aspects of his theory. One of these was the difference in heat during expansion of a gas. They found that when an amount of gas was allowed to expand in a vacuum it tended to lose heat. They explained it in terms of heat-to-work, but it is now recognized as a property of the molecules separating one from another. By investigating this principle, industrialists founded the principles necessary to begin the refrigeration industry by the turn of the twentieth century.
Though it did not receive much recognition at the time, Joule's study of the velocity of gas molecules did much to encourage the kinetic theory of gases. His interest had been developed by the tutor from his teens, John Dalton. By this time, Joule was well recognized for his detailed thoughts and precise measurements. To have such a distinguished scientist present findings supporting the theory encouraged other researchers.
Joule received many awards in his lifetime. After presenting his research to the Royal Society in 1849, he was elected a fellow. As a member of the society, he earned the Royal medal and the honored Copley medal for the same research. It was well noted that this was a very rare achievement, to win both for the same research. Another honored event occurred when his family's industry went broke. The queen herself offered him a pension. However, the most treasured award he received was perhaps the first, when he was reunited with Dalton at his first meeting of the Literary and Philosophical society. Dalton recognized how impressed the audience was and uncharacteristically asked the audience to applaud the young man. This applause, though faded for many years, eventually included the nation.
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