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John Henry Poynting
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Poynting, John Henry
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Michael Faraday (L) English physicist and chemist (electromagnetism) and John Frederic Daniell (R) British chemist and meteorologist who invented the Daniell cell.
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Italian-born physicist Dr. Enrico Fermi draws a diagram at a blackboard with mathematical equations. circa 1950.
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Born:
September 9, 1852, Monton, Lancashire, England
Died:
March 30, 1914, Birmingham, Warwickshire (aged 61)
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John Henry Poynting

British physicist
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John Henry Poynting (born September 9, 1852, Monton, Lancashire, England—died March 30, 1914, Birmingham, Warwickshire) was a British physicist who introduced a theorem that assigns a value to the rate of flow of electromagnetic energy known as the Poynting vector.

He was a professor of physics at Mason Science College (later the University of Birmingham) from 1880 until his death. In papers published in 1884–85, he showed that the flow of energy at a point can be expressed by a simple formula in terms of the electric and magnetic forces at that point. This is Poynting’s theorem. He also wrote papers on radiation and the pressure of light. After 12 years of experiments he determined in 1891 the mean density of the Earth and in 1893 the gravitational constant, a measure of the effect of gravity. He published his results in The Mean Density of the Earth (1894) and The Earth; Its Shape, Size, Weight and Spin (1913).

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