Question

What was the contribution of Joule in understanding the laws of Thermodynamics?

Answer 1

James Prescott Joule was born at Salford, near Manchester, England, on December 24, 1818.He gave us first law of thermodynamics—that energy can neither be created nor destroyed—"one of the very important laws of nature".

Experiments:

From 1839, Joule began a series of experiments involving mechanical work, electricity and heat. In 1840, he showed that the amount of heat produced per second in a wire carrying an electric current equals the current (I) squared multiplied by the resistance (R) of the wire. The heat produced is the electric power lost (P). (That is, P=I²R.) This relationship is known as Joule’s Law.

In 1843, Joule calculated the amount of mechanical work needed to produce an equivalent amount of heat. This quantity was called “the mechanical equivalent of heat.

But in that time, Many British scientists were hesitant to accept his work and Joule’s work on the relationship of heat, electricity and mechanical work was largely ignored until 1847. But Joule patiently persisted. New ideas often take time to gain acceptance, especially if they are put forward by an amateur in that field. Joule’s findings challenged the caloric theory of heat which most physicists believed in at that time. In the caloric theory, heat was believed to be a fluid substance.

In 1847, his work then came to the attention of William Thomson. (Thomson, who was later known as Lord Kelvin, was another famous scientist who was a committed Christian). Thomson recognized that Joule’s work fitted in with the unifying pattern that was beginning to emerge in physics and he enthusiastically endorsed Joule’s work. (In fact, Joule’s work made a significant contribution to the process of unifying the fragmented sections of physics).

New Scientific Discipline—Thermodynamics

The principle of energy conservation involved in Joule’s work gave rise to the new scientific discipline known as thermodynamics.

While Joule was not the first scientist to suggest this principle, he was the first to demonstrate its validity. Although Thomson and a number of other scientists later made significant contributions to thermodynamics, Joule is correctly recognized as the chief founder of thermodynamics. He showed that “work can be converted into heat with a fixed ratio of one to the other, and that heat can be converted into work.

Joule’s principle of energy conservation formed the basis of the first law of thermodynamics. This law states that energy can neither be created nor destroyed, but it can be changed from one form into another.

dQ-dW=dU

This law is a result of the famous experiments James Joule conducted in the 1840s that identified heat as a form of energy having a unique equivalence to work.