机电一体化专业英语教学课件 作者 黄星 夏玉波 Unit 7.pptVIP

Part I Technical and Practical Reading Passage A Electronic Components and Symbols An electronic component is a basic electronic element and is usually packaged in a discrete form with two or more connecting leads or metallic pads. Components are intended to be connected together, usually by soldering to a printed circuit board, to create an electronic circuit with a particular function (for example an amplifier, radio receiver, or oscillator). There are a large number of symbols which represent an equally large range of electronic components. It is important that you can recognize the more common components and understand what they actually do. Diodes Diodes are basically a one-way valve for electrical current. They let it flow in one direction (from positive to negative) and not in the other direction.? Most diodes are similar in appearance to a resistor and will have a painted line on one end showing the direction or flow (white side is negative). If the negative side is on the negative end of the circuit, current will flow. If the negative is on the positive side of the circuit, no current will flow. Transistors There are two types of standard transistors, NPN and PNP, with different circuit symbols. The transistor is possibly the most important invention of this decade.? It performs two basic functions. 1) It acts as a switch turning current on and off. 2) It acts as an amplifier. This makes an output signal that is a magnified version of the input signal. Resistors Resistors, like diodes and relays, are another of the electronic parts that should have a section in the installers parts bin. They have become a necessity for the mobile electronics installer, whether it be for door locks, timing circuits, remote starts, LEDs, or just to discharge a stiffening capacitor. Resistors resist the flow of electrical current. The higher the value of resistance (measured in ohms) the lower the current will be. Capacitors A de