Heinrich Barkhausen, German physicist, c 1920s.
© Science Museum / Science & Society Picture Library
Barkhausen (1881-1956) was appointed profesor of low current technology at the Technische Hochschule, Dresden, Germany in 1911. His discovery that the magnetisation of iron happens in discrete stages gained him the Heinrich Hertz medal in 1928. Barkhausen devised a loudspeaker in order to make the discontinuity in the magnetisation of iron; the audible phenomenon became known as the Barkhausen effect. He also carried out research on electron tubes and electrical oscillations.