時間：2011-03-11 23:18來源：藍(lán)天飛行翻譯 作者：航空 點擊：次
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residual magnetic particle inspection. A form of magnetic particle inspection for small steel parts that have a high degree of retentivity. The part is magnetized, then removed from and inspected away from the magnetizing machine. residual magnetism (electric generator). The magnetism that remains in the field frame of a generator when no current is flowing in the field coils. It is residual magnetism that produces the initial current when a generator begins to turn. As soon as the current produced by the residual magnetism begins to flow in the field coils, the field strength increases and more current is produced. resin (natural). A natural, translucent, solid or semisolid material, produced from the sap of certain trees or plants. Resins are soluble in organic solvents, such as ether, but are not soluble in water. Resins are used in the manufacture of varnishes, inks, and certain types of plastics. resistance, R (electrical characteristic). The characteristic of an electrical circuit that opposes the flow of electrons. When electrons flow through a resistance, power is used, voltage is dropped, and, generally, heat is produced. The amount of resistance in a circuit is measured in ohms, with one ohm being the amount of resistance needed to produce a one-volt drop when one amp of current flows through it. resistance decade (electronic equipment). A piece of electronic test equipment consisting of several precision resistors and selector switches. By connecting the resistance decade into a circuit and setting the selector switches in the proper positions, any required amount of resistance can be put into a circuit. The resistance decade gets its name from the increments of resistance that can be selected. One switch can select resistances between 0.0 ohm and 0.9 ohm, in ten steps (a decade of steps) of 0.1 ohm each. The next switch can select resistances between 1.0 and 9.0 ohms. The other switches can select between 10.0 and 90.0, 100.0 and 900.0, and 1,000 and 9,000 ohms. With five switches, any amount of resistance between 0.1 ohm and 9,999.9 ohms can be put into a circuit. resistance furnace. A type of furnace used for making alloys of certain metals. The heat that melts the metal is produced by passing a large amount of electrical current through it. resistance thermometer. A type of electrical temperature-measuring instrument that uses a resistance bulb as its temperature-sensing element. The resistance bulb contains a length of small diameter nickel wire, wound on a mica form and enclosed in a thin stainless steel tube. The resistance of the nickel wire increases as its temperature increases. The resistance bulb is installed in a Wheatstone bridge circuit in such a way that current flowing through the indicating instrument changes as the resistance of the bulb changes. resistance welding. A form of electrical welding used for joining thin sheets of metal. The metal to be welded is pressed together by the electrodes of the welding machine, and low-voltage current is passed through the metal. |
