翻訳と辞書 Words near each other ・ Fleming of Louhisaari ・ Fleming Park (Missouri) ・ Fleming Park Bridge ・ Fleming Park, Alberta ・ Fleming Peaks ・ Fleming Point ・ Fleming River ・ Fleming Road ・ Fleming Stadium ・ Fleming Summit ・ Fleming Township, Aitkin County, Minnesota ・ Fleming Township, Minnesota ・ Fleming Township, Pine County, Minnesota ・ Fleming v Beevers ・ Fleming v Securities Commission ・ Fleming valve ・ Fleming Williams ・ Fleming's left-hand rule for motors ・ Fleming's Prime Steakhouse & Wine Bar ・ Fleming's right-hand rule ・ Fleming, Colorado ・ Fleming, Georgia ・ Fleming, Indiana ・ Fleming, Kansas ・ Fleming, Kentucky ・ Fleming, Missouri ・ Fleming, New York ・ Fleming, Ohio ・ Fleming, Saskatchewan ・ Fleming, West Virginia Dictionary Lists mini英和辞書 mini和英辞書 Webster 1913 Latin-English FOLDOC Wikipedia English ウィキペディア

翻訳と辞書　辞書検索 [ 開発暫定版 ] スポンサード リンク Fleming valve ： ウィキペディア英語版 Fleming valve The Fleming valve, also called the Fleming oscillation valve, was a vacuum tube (or "thermionic valve") invented in 1904 by John Ambrose Fleming as a detector for early radio receivers used in electromagnetic wireless telegraphy. It was the first practical vacuum tube and the first thermionic diode, a vacuum tube whose purpose is to conduct current in one direction and block current flowing in the opposite direction. The thermionic diode was later widely used as a rectifier — a device which converts alternating current (AC) into direct current (DC) — in the power supplies of a wide range of electronic devices, until largely replaced by the semiconductor diode in the 1960s. The Fleming valve was the forerunner of all vacuum tubes, which dominated electronics for 50 years. The IEEE has described it as "one of the most important developments in the history of electronics", and it is on the List of IEEE Milestones for electrical engineering. ==How it works== The valve consists of an evacuated glass bulb containing two electrodes: a cathode in the form of a "filament", a loop of carbon or fine tungsten wire, similar to that used in the light bulbs of the time, and an anode (plate) consisting of a sheet metal plate. Although in early versions the anode was a flat metal plate placed next to the cathode, in later versions it became a metal cylinder surrounding the cathode. In some versions, a grounded copper screen surrounded the bulb to shield against the influence of external electric fields. In operation, a separate current flows through the cathode "filament", heating it so that some of the electrons in the metal gain sufficient energy to escape their parent atoms into the vacuum of the tube, a process called thermionic emission. The AC current to be rectified is applied between the filament and the plate. When the plate has a positive voltage with respect to the filament, the electrons are attracted to it and an electric current flows from filament to plate. In contrast, when the plate has a negative voltage with respect to the filament, the electrons are not attracted to it and no current flows through the tube (unlike the filament, the plate does not emit electrons). As current can pass through the valve in one direction only, it therefore "rectifies" an AC current to a pulsing DC current. This simple operation was somewhat complicated by the presence of residual air in the valve, as the vacuum pumps of Fleming's time were unable to create as high a vacuum as exists in modern vacuum tubes. At high voltages, the valve could become unstable and oscillate, but this occurred at voltages far above those normally used. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Fleming valve」の詳細全文を読む スポンサード リンク 翻訳と辞書 : 翻訳のためのインターネットリソース Copyright(C) kotoba.ne.jp 1997-2016. All Rights Reserved.