John Sealy Townsend

Sir John Sealy Edward Townsend ( born June 7, 1868 in Galway, County Galway, Ireland, † February 16, 1957 in Oxford ) was a British physicist.

Life and work

Townsend studied at Trinity College, Cambridge. He was a research student in the Cavendish Laboratory under JJ Thomson. Since 1900 he was a professor at Oxford.

Townsend yielded significant works to the electrical conductivity of gases ( Townsend discharge Townsend or current). 1897 was appointed as the first the elementary electric charge with his development of the droplet method. This method was later used by Robert Andrews Millikan improved ( Millikan experiment ). In 1901 he discovered the ease of ionization of molecules by ion impact and the dependence of the mean free path of electrons ( in gases ) of the energy ( Ramsauer - Townsend effect).

1903 Townsend was admitted as a member of the Royal Society.

Honors

According to him, the physical unit Townsend ( Td) is named, in the so-called reduced electric field strength (ratio of electric field strength and particle density ) is measured:

Writings (selection )

• The Theory of Ionization of Gases by Collision. , 1910.
• Motion of Electrons in the gas. In 1925.
• Electricity and radio transmission. , 1943.
• Electromagnetic Waves. In 1951.