時(shí)間：2011-03-11 23:18來源：藍(lán)天飛行翻譯 作者：航空 點(diǎn)擊：次
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As the wipers move across the transmitter resistor, the current in the three sections of the indicator coil change. The changing current changes the magnetic field produced by the coil so the magnet to which the pointer is attached moves in exactly the same way as the shaft in the transmitter. selvage edge (fabric). The woven edge of fabric used to prevent the material unraveling during normal handling. The selvage edge, which runs the length of the fabric parallel to the warp threads, is normally removed from materials before they are used in composite construction. semi. A prefix meaning partially or part (usually half) of something. A semicircle is half of a circle, and a semiannual event is something that takes place every half year (twice in a year). semiautomatic operation. An operation that is partially automatic. Some manual input is needed to start the operation, but once started, it completes its cycle of operation with no further input. semiconductor. A material whose electrical conductivity is between that of an insulator and a conductor. The electrical properties of a semiconductor are caused by its atomic structure and by the way the material has been processed. Valence electrons are the electrons in the outer shell of an atom, and the number of valence electrons is the important characteristic of the atomic structure of a semiconductor material. Silicon and germanium, the two chemical elements most often used for semiconductor devices, both have four valence electrons. An important step in the production of semiconductor materials is that of “doping,” which is the addition of minute amounts of other chemical elements, called impurity elements, which have either three or five valence electrons. Just a few parts per million of these impurity elements cause the semiconductor material to act as either a conductor or an insulator, depending upon the polarity of the voltage placed across it. semiconductor diode. A two-element, solid-state electron check valve made of silicon or germanium, doped with appropriate impurities. Electrons can either flow through a semiconductor diode or not flow through it depending upon the polarity of the voltage across it. When the diode is forward-biased, with the positive voltage connected to the anode, and the negative voltage to the cathode, electrons flow through it. But, when it is reverse-biased, with the negative voltage connected to the anode, electrons do not flow through it. semiconductor integrated circuit. A complex electronic circuit made on a single chip of semi-conductor material. Passive components, such as resistors and capacitors, and active components such as transistors are formed by several layers of conducting and insulating materials. These components are connected together to form such complete circuits as gates and amplifiers. |
