自动化专业英语期末复习课文与翻译(5页).doc
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1、-自动化专业英语期末复习课文与翻译-第 5 页 An electrical circuit or network is composed of elements such as resistors , inductors , and capacitors connected together in some manner .If the network contains no energy sources , such asbatteries or electrical generators,it is known as a passive network.On the other hand,
2、 if one or more energy sources are present , the resultant combination is an active network. In studying the behavior of an electrical network,we are interested in determining the voltages and currents that exist within the circuit. Since a network is composed of passive circuit elements,we must fir
3、st define the electrical characteristics of these elements.电路或电网络由以某种方式连接的电阻器、电感器和电容器等元件组成。如果网络不包含能源,如电池或发电机,那么就被称作无源网络。换句话说,如果存在一个或多个能源,那么组合的结果为有源网络。在研究电网络的特性时,我们感兴趣的是确定电路中的电压和电流。因为网络由无源电路元件组成,所以必须首先定义这些元件的电特性. In the case of a resistor, the voltage-current relationship is given by Ohms law, which
4、ststes that the voltage across the resistor is equal to the current through the resistor multiplied by the value of the resistance. Mathematically, this is expressed as u=iR where u=voltage , V; i=current, A; R=resistance .就电阻来说,电压-电流的关系由欧姆定律给出,欧姆定律指出:电阻两端的电压等于电阻上流过的电流乘以电阻值。在数学上表达为:u=iR (1-1A-1)式中 u
5、=电压,伏特;i =电流,安培;R = 电阻,欧姆。 The voltage across a pure inductor is defined by Faradays law ,which states that the voltage across the inductor is proportional to the rate of change with time of the current through the inductor. Thus we have u=Ldi/dt where di/dt=rate of change of current ,A/s; L=inducta
6、nce ,H. 纯电感电压由法拉第定律定义,法拉第定律指出:电感两端的电压正比于流过电感的电流随时间的变化率。因此可得到:U=Ldi/dt 式中 di/dt = 电流变化率, 安培/秒; L = 感应系数, 享利。 The voltage developed across a capacitor is proportional to the electric charge q accumulating on the plates of the capacitor. Since the accumulation of charge may be expressed as the summatio
7、n, or integral , of the charge increments dq, we have the equation u=1/c fdq where the capacitance C is the proportionality constant relating voltage and charge. By definition, current equals the rate of change of charge with time and is expressed as i=dq/dt. Thus an increment of charge dq is equal
8、to the current multiplied by the corresponding time increment, or dq=i dt. 电容两端建立的电压正比于电容两极板上积累的电荷q 。因为电荷的积累可表示为电荷增量dq的和或积分,因此得到的等式为 u= 1/c fdq,式中电容量C是与电压和电荷相关的比例常数。由定义可知,电流等于电荷随时间的变化率,可表示为i = dq/dt。因此电荷增量dq 等于电流乘以相应的时间增量,或dq = i dt, 那么等式 (1-1A-3) 可写为式中 C = 电容量,法拉。 A common method of analyzing an el
9、ectrical network is mesh or loop analysis. The fundamental law that is applied in this method is Kirchhoffs first law, which states that the algebraic sun of the voltages around a closed loop is 0 ,or , in any closed loop , the sum of the voltage rises must equal the sum of the voltage drops. Mesh a
10、nalysis consists of assuming that currents-termed loop currents-flow in each loop of a network ,algebraically summing the voltage drops around each loop ,and setting each sum equal to 0. 分析电网络的一般方法是网孔分析法或回路分析法。应用于此方法的基本定律是基尔霍夫第一定律,基尔霍夫第一定律指出:一个闭合回路中的电压代数和为0,换句话说,任一闭合回路中的电压升等于电压降。网孔分析指的是:假设有一个电流即所谓的回
11、路电流流过电路中的每一个回 路,求每一个回路电压降的代数和,并令其为零 One problem with electronic devices corresponding to the generalized amplifiers is that the gains, Au or Ai, depend upon internal properties of the two-port system(u,,Ri ,Ro, etc). This makes design difficult since these parameters usually vary from device ,as wel
12、l as with temperature. The operational amplifier, or Op-Amp, is designed to minimize this dependence and to maximze the ease of design. An Op-Amp is an integrated circuit that has many component parts such as resistors and transistors built into the device. At this point we will make no attempt to d
13、escribe these inner workings. 运算放大器像广义放大器这样的电子器件存在的一个问题就是它们的增益AU或AI取决于双端口系统(m、b、RI、Ro,等)的内部特性。器件之间参数的分散性和温度漂移给设计工作增加了难度。设计运算放大器或Op-Amp的目的就是使它尽可能的减少对其内部参数的依赖性、最大程度地简化设计工作。运算放大器是一个集成电路,在它内部有许多电阻、晶体管等元件。就此而言,我们不再描述这些元件的内部工作原理。 Integrated circuit technology allows construction of many amplifier circuits
14、 on a single composite chip of semiconductor material.集成电路技术使得在非常小的一块半导体材料的复合 “芯片”上可以安装许多放大器电路。 The first law states that in normal Op-Amp circuits we may assume that the voltage difference between the input terminals is zero, that is , U+=U-第一个定律指出:在一般运算放大器电路中,可以假设输入 端间的电压为零,也就是说U+=U-The second law
15、 states that in normal Op-Amp circuits both of the input currents may be assumed to be zero: I+=I-=0第二个定律指出:在一般运算放大器电路中,两个输入电流可被假定为零:I+=I-=0 The two-valued variables which we have been discussing are often called logical variables, while the operations such as the OR operation and the AND operation
16、are referred to as logical operations. We shall now briefly discuss the relevance of such terminology, and in so doing we shall bing out the special aptness of the designations true and false to identify the possible values of a variable.逻辑变量我们讨论的双值变量通常叫做逻辑变量,而象或和与这样的操作被称为逻辑操作。现在我们将简要地讨论一下这些术语之间的关联,
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