John Sealy Edward Townsend (7 June 1868 - 16 February 1957) was a mathematical physicist who conducted various studies concerning the electrical conduction of gases (concerning the kinetics of electrons and ions) and directly measured the electrical charge. He was a Wykeham Professor of physics at Oxford University.
Career
He was born in Galway, County Galway, Ireland, son of Edward Townsend, a Professor of Civil Engineering at Queen's College, Galway. In 1885, he entered Trinity College Dublin and came top of the class in maths with a BA in 1890. He became a Clerk Maxwell Scholar and entered Trinity College, Cambridge where he became a research student at the same time as Ernest Rutherford. At the Cavendish laboratory, he studied under J. J. Thomson. He developed the "Townsend's collision theory". Townsend supplied important work to the electrical conductivity of gases ("Townsend discharge" circa 1897). This work determined the elementary electrical charge with the droplet method. This method was improved later by Robert Andrews Millikan.
In 1900, he became a professor at Oxford. In 1901, he discovered the ionization of molecules by ion impact and the dependence of the mean free path on electrons (in gases) of the energy (and his independent studies concerning the collisions between atoms and low-energy electrons in the 1920s would later be called the Ramsauer-Townsend effect). On June 11, 1903, he was elected to Fellow of the Royal Society (FRS). He was awarded the Hughes Medal in 1914. During World War I, he researched (at Woolwich, London, England) wireless methods for the Royal Navy Air Service. He was knighted in 1941. He died in Oxford, England.
He married May Georgina, also from County Galway, and they had two sons.
Townsend was a laboratory demonstrator when Brebis Bleaney was an undergraduate. Bleaney recounts an occasion when Townsend gathered together all the demonstrators and proceeded to refute both quantum mechanics and relativity.
Works
- The Theory of Ionisation of Gases by Collision (1910)
- Motion of Electrons in Gases (1925)
- Electricity and Radio Transmission (1943)
- Electromagnetic Waves (1951)
Show/Hide comment form
