Q: Why do birds fly south for the winter?
A: It's too far to walk.
Sir Ambrose FlemingDied 18 Apr 1945 at age 95 (born 29 Nov 1849). John Ambrose Fleming was an English electrical engineer who invented, and coined the name for, the first thermonic valve (also known as a vacuum tube). It was a diode with two electrodes, that acted as a rectifier, restricting current to flow in only one direction in a circuit (patented 1904). It made use of the Edison effect— the emission of electrons from a heated metal surface. By sealing a heated filament in a glass envelope containing a vacuum, the internal movement of electrons was not obstructed by gas molecules. The second electron at high positive voltage attracted the electrons released from the surface of the first, heated, electrode. It was applied the device in circuits for the nacent telecommunications industry. His name is remembered in the Fleming “Left Hand Rule” mnemonicfor relating the directions of motion, current and magnetic field for a motor.« |
