John Henry Poynting
Poynting, John Henry (1852-1914) was a British physicist who created a theorem, known as the Poynting vector, that gives a value to the rate of flow of electromagnetic energy.
Poynting was born Sept. 9, 1852, in Monton, near Manchester, England. He was educated at Owens College (now the University of Manchester), London University, and Trinity College, Cambridge. He became professor of physics at Mason College (later the University of Birmingham) in 1880, where he remained until his death.
In 1884, Poynting introduced the Poynting vector, which provides a simple equation for the rate of flow of electromagnetic energy. Together, changing electric and magnetic fields make electromagnetic waves, also called electromagnetic radiation. These electromagnetic waves carry energy, known as electromagnetic energy, at the speed of light as they move through empty space. The energy the waves transport per unit area per unit time is described by the Poynting vector. Light, radio and TV signals, and microwaves all consist of electromagnetic waves.
Poynting performed research on electrical phenomena. He also studied the changes between solid and liquid states of matter. He studied osmotic pressure in 1896. Osmotic pressure is the force acting upon a semipermeable membrane placed between a solution and a pure solvent, such as water, caused by the flow of solute molecules through the membrane toward the pure solvent.
Poynting wrote On the Mean Density of the Earth (1893), for which he was awarded the Adams prize at Cambridge, and he co-authored the two-volume Textbook of Physics (1899, 1914). He also wrote The Earth: Its Shape, Size, Weight and Spin (1913).
Poynting was elected Fellow of the Royal Society in 1888, and in 1905 he was awarded the Royal Society's Royal Medal and elected president of the Physical Society. He died March 30, 1914, in Birmingham, Warwickshire, England.