- Townsend , Sir John Sealy Edward
- (1868–1957) Irish physicistTownsend, the son of a professor of civil engineering from Galway (now in the Republic of Ireland), was educated at Trinity College, Dublin. In 1895 he took advantage of a change in the Cambridge examination statutes and, together with Ernest Rutherford, entered the Cavendish Laboratory as one of the first two non-Cambridge graduates. There they worked as research students of J.J. Thomson. In 1900 Townsend moved to Oxford as the first Wykeham Professor of Experimental Physics, a post he retained until his retirement in 1941.In 1898 Townsend achieved his first major scientific success when he measured the fundamental unit of electric charge (the charge of the electron). The previous year Thomson had reported the discovery of the electron, whose mass he estimated at about 1/1000 that of the hydrogen atom. Townsend, working with gases released by electrolysis, was able to form charged clouds of water droplets and, by measuring the rate of fall of a water drop in the cloud, he could calculate the charge on each drop. More accurate work of this type was done by Robert Millikan in 1911.Townsend's main work however was on, to take the title of his important book, Electricity in Gases (1915). He formulated a theory of ionization by collision, showing that the motion of electrons in an electric field would release more electrons by collision. These in turn would release even more electrons, and so on. This multiplication of charges, known as an avalanche, allowed him to explain the passage of currents through gases where the electric field was thought to be too weak.Townsend was knighted in 1941.
Scientists. Academic. 2011.
Look at other dictionaries:
Townsend, Sir John Sealy Edward — ▪ British physicist born June 7, 1868, Galway, County Galway, Ire. died Feb. 16, 1957, Oxford British physicist who pioneered in the study of electrical conduction in gases and made the first direct measurement of the unit electrical charge … Universalium
John Sealy Edward Townsend — John Sealy Townsend. Sir John Sealy Edward Townsend (* 7. Juni 1868 in Galway, County Galway, Irland; † 16. Februar 1957 in Oxford) war ein britischer Physiker. Townsend studierte am Trinity Coll … Deutsch Wikipedia
John Sealy Townsend — Sir John Sealy Edward Townsend (* 7. Juni 1868 in Galway, County Galway, Irland; † 16. Februar 1957 in Oxford) war ein britischer Physiker. Townsend studierte am Trinity College in … Deutsch Wikipedia
John Sealy Townsend — Infobox Scientist box width = 300px name = John Townsend image size = 300px caption = John Sealy Edward Townsend (1868 1957) birth date = birth date|1868|6|7|mf=y birth place = Galway, County Galway, Ireland death date = death date|1957|2|16|mf=y … Wikipedia
Townsend — [ təʊnzend], Sir (seit 1941) John Sealy Edward, britischer Physiker, * Galway 7. 6. 1868, ✝ Oxford 16. 2. 1957; 1900 41 Professor in Oxford. Townsend gelang 1898 die Bestimmung der Elementarladung mittels einer Tröpfchenmethode, ab 1900… … Universal-Lexikon
Électron — Traduction à relire Electron → … Wikipédia en Français
Scientific phenomena named after people — This is a list of scientific phenomena and concepts named after people (eponymous phenomena). For other lists of eponyms, see eponym. NOTOC A* Abderhalden ninhydrin reaction Emil Abderhalden * Abney effect, Abney s law of additivity William de… … Wikipedia
Liste der Biografien/To — Biografien: A B C D E F G H I J K L M N O P Q … Deutsch Wikipedia
List of people from Kent — List of notable residents of the county of Kent in England. Persons are grouped by occupation and listed in order of birth. Kent is defined by its current boundaries.Politicians, statesmen and lawyers*John Scott of Scott s Hall (–1485) – Lord… … Wikipedia
1957 in Ireland — Events*January 1 Seán South and Fergal O Hanlon are killed in an IRA attack on an RUC barracks in Brookeborough, County Fermanagh. The two men become part of republican folklore. *January 24 Sir Alfred Chester Beatty becomes the first honorary… … Wikipedia