2006-10-25 07:22:10 · 7 answers · asked by Anonymous in Science & Mathematics ➔ Engineering
Please don't be retarded like Nelly and lucky...
2006-10-25 07:30:37 · update #1
they SUCK lol
2006-10-25 07:23:52 · answer #1 · answered by nelly 2 · 0⤊ 3⤋
What others have said. They are forerunners of transistors, but more specifically act much like a combination of field effect transistor (FET) in series with a diode. A typical tube has the following parts: a cathode, a cathode heater, one or more grids, and an anode (or plate). Some tubes have no grids and simply act like diodes. Others have one or more grids and have names related to the number of active elements (everything's active but the cathode heater, which isn't active in the sense of how the tube works in a circuit), such as triodes (3 - cathode, grid, plate), tetrode (4 - cathode, 2 grids, plate), etc.
In typical use, the cathode in the tube is heated by the filament, which causes it to boil off electrons into the surrounding vacuum by thermionic emmission. The tube's plate, when positively charged in relation to the cathode attracts the cathode's electrons to it. Since the plate doesn't emit electrons, current only flows one way (that being the diode action).
If present, the grids are located between the cathode and the plate. The grids are screens and have sufficient gaps to allow the electrons to flow relatively unimpeded from the tube's cathode to the tube's plate. If a negative voltage relative to the cathode is applied to a grid, electron flow from the cathode to the plate can be limited, or shut off. Similarly, the grid voltage can be modulated, which will cause the current on the plate to modulate as well. This is the basis for using tubes as amplifiers.
2006-10-25 15:28:26 · answer #2 · answered by billclawson 2 · 2⤊ 0⤋
They were the forerunners of the transistors. A heated cathode had its electrons literally boiled off it. A positively charged anode attracted the electrons. Intermediate grids, if there were any, could modulate the flow of electrons, and thus amplify a signal.
2006-10-25 14:30:35 · answer #3 · answered by Sqdr 3 · 2⤊ 0⤋
They were a form of electrical switch before the transistor became common.
2006-10-25 14:30:52 · answer #4 · answered by kate 7 · 0⤊ 0⤋
to you unify the current and convert it from AC to DC as transistors
2006-10-25 15:10:24 · answer #5 · answered by source_of_love_69 3 · 0⤊ 1⤋
It gives you a good suction.
2006-10-25 14:27:14 · answer #6 · answered by Anonymous · 0⤊ 3⤋
they SUCK!!!! lol
2006-10-25 20:03:16 · answer #7 · answered by Nate 1 · 0⤊ 2⤋