James Prescott Joule

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- James Prescott Joule -

- Born: 1818 Died 1889 -

Joule's career in the sciences began quite early in his life. As early as 16, Prescott was under the tutelage of James Dalton. His experiments soon followed in a laboratory he built in his family's basement. By this time, many scientists had begun hypothesizing on the interrelationships between heat, electricity, and magnetism - and by the 1840's Joule had formulated not only the well known "Joule's Law" but also a principle for conservation of energy. In the 1850's, Joule worked together with another scientist to come up with the "Joule-Thomson effect".

Possibly his most well-known experiment is his "Paddle wheel" experiment, which led to an understanding of the conversion of energy from one form to another.

His experimentations were not limited to simply those bounded in the areas of physics. Joule was an inventor as well - his accomplishments included the "arc" welding process and a displacement pump.

As with every scientist, there is a list of Joule's failures. He attempted to design a motor that would provide infinite power but after many failed attempts realized it was unobtainable.

- Joule's Law -

- 1840 -

Simply stated, Joule's Law relates how heat is dissipated by a resistor. Joule's Law states that the heat given off is equal to the square of the current multiplied by the resistance of the resistor and the amount of time passed.

This law also relates itself to Thermodynamics, stating that "at constant temperature the internal energy of an ideal gas is independent of volume."1

- Paddle Wheel Experiment -

- 1849 -

This experiment involved the dropping of weights from a specific height; these weights would churn the water inside of the bucket and increase the overall temperature of the water slightly. This relationship served as the foundation to the First Law of Thermodynamics:

- Joule-Thomson Effect -

Although relatively easy to grasp for anyone in Physics, this discovery was key in understanding the relationships between pressure of gas and its temperature. The Joule-Thomson Effect shows that an insulated gas will lower its temperature as the pressure is decreased without doing any work.

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