电子与通信技术专业英语Unit-I-2课件.ppt

1、Unit I Basic Knowledge of ElectronicsLesson 2 Current, Voltage and ResistanceNew Words conductor kndkt n. 导体，导线 symbol simbl n. 符号，标志, 象征 ampere mp n. 安培 coulomb ku:lm n. 库仑 Magnitude mgnitju:d n. 大小，数量, 巨大，广大 equivalent ikwivlnt a.相等的, 相同的， 等量的 volt vult n. 伏特 Phrases and Expressions electromotive

2、force 电动势 electric current 电流Notes1.The flow of electrons through a conductor is called a current. 通过导体的电子流称为电流。2.The basic unit in which current is measured is the ampere (amp). 度量电流的基本单位是安培。 句中in which current is measured 是定语从句定语从句，修饰unit。3.to be defined as：给下定义为，后可接名词或宾语从句后可接名词或宾语从句, ,如课文第四段如课文第四

3、段。 4.When it is desirable to express a magnitude of current smaller than the ampere it是形式主语形式主语，不定式to express a magnitude of current smaller than the ampere充当真正的主语。5. required cause a current of one ampere to pass through a conductor having a resistance of one ohm 过去分词required充当后置定语后置定语，修饰electromot

4、ive force；having a resistance of one ohm是现在分词短语，充当后置定语，修饰conductor。 6. term that is often expressed by using . 此为ohm的同位语同位语，其中that is often expressed by using 是定语从句定语从句，修饰term。7. that will limit the current in a conductor is one ampere when the voltage applied to the conductor is one volt. 定语从句定语从句，

5、修饰amount of resistance，其中when the voltage applied to the conductor is one volt是时间状语从句时间状语从句。8.The relationship between volts, amperes，and the ohms can be represented by “Ohms Law”. 伏特、安培和欧姆之间的关系可用欧姆定律表示。 欧姆定律，即：电阻等于电压除以电流，即：R=U/I (U=IR 或 I=U/R)Translation of TextsLesson 2 Current, Voltage and Resist

6、ance The flow of electrons through a conductor is called a current. Current flow is represented by the letter symbol I. The basic unit in which current is measured is the ampere (amp). One ampere of current is defined as the movement of one coulomb (6.281018 electrons) past any point of a conductor

7、during one second of time. 第第2课课 电流、电压和电阻电流、电压和电阻 通过导体的电子流称为电流。电流用字母符号I表示。度量电流的基本单位是安培。1安培电流的定义是：在1秒钟内有1库伦（6.28108电子）的电量通过导体的任何一点时电流为1安培。 When it is desirable to express a magnitude of current smaller than the ampere, the milliampere (mA) and the microampere (A) units are used. One milliampere is eq

8、uivalent to one-thousandth (0.001) of an ampere, and one microampere is equivalent to one-millionth (0.000001) of an ampere. 当需要表示比安培小的电流量时，可用毫安（mA）和微安（A）表示。毫安等于千分之一安培，1微安等于百万分之一安培。 The term voltage (represented by the letter symbol V) is commonly used to indicate both a difference in potential and

9、an electromotive force. The unit in which voltage is measured is the volt. One volt is defined as that magnitude of electromotive force required cause a current of one ampere to pass through a conductor having a resistance of one ohm. 电压这个术语（用字母符号U表示）常用来表示电位差和电动势。度量电压的单位是伏特。使1安培电流流过电阻为1欧姆的导体所需的电动势定义

10、为1伏特。 A magnitude of voltage less than one volt is expressed in terms of millivolts (mV) or microvolts (V). Larger magnitudes of voltage are expressed in kilovolts (kV). One kilovolt equals one thousand volts. 小于1V的电压值用毫伏(mV)或微伏( V )表示。较高的电压值可用千伏(kV)表示。1kV等于1000V。 The opposition to current is called

11、 electrical resistance and is represented by the letter symbol R. The unit of resistance is the ohm, a term that is often expressed by using . One ohm is defined as that amount of resistance that will limit the current in a conductor is one ampere when the voltage applied to the conductor is one vol

12、t. Larger amounts of resistance are commonly expressed in kiloohm (k) and in megohm (M ). 对电流的阻力叫电阻, 用字母符号R表示。电阻的单位是欧姆，常用表示。1欧姆的定义是：当加到导体上的电压为1伏特时，将导体中的电流限制为1安培所需的电阻值。较大的电阻值常用千欧( k )和兆欧（M）表示。 The relationship between volts, amperes, and ohms can be represented by “ Ohms Law”. Ohms Law states that th

13、e ratio of the voltage between the ends of a wire and the current flowing in it is equal to the resistance of the wire. Now, we can say that when a given voltage is applied across the ends of the wire, an electric current always flows along it, and the value of this current depends on the resistance

14、 of wire (as shown in fig.2-1). 伏特、安培和欧姆之间的关系可用欧姆定理表示。欧姆定律描述为：导线两端电压与流过导线的电流的比是导线的电阻。现在我们可说，当在导线两端施加一定电压时，导线中总是有电流，电流的值取决于导线的电阻（如图2-1所示）。Exercises1.Write T (true) or F (false) beside the following statements about the text.a. Current flow is represented by the letter symbol I.b. One milliampere is e

15、quivalent to onethousandth(0.001)of an ampere，and one microampere is equivalent to one-billionth(0.000 000 001)of an ampere.c. The term voltage is commonly used to indicate a difference in potential bat electromotive force is not.dOne kilovolt equals one thousand volts.e. The opposition to current i

16、s called electrical resistance。f. larger amounts of resistance are commonly expressed in kiloohm (k) and in megohm (M).g. The flow of electrons through a conductor is called a resistance.h. One volt is defined as that magnitude of electromotive force required cause a current of one ampere to pass th

17、rough a conductor having a resistance of one ohm.2.Match the following terms to appropriate definition or expression.a. current 1.electromotive force b. amp 2.The relationship between volts, amperes, and ohms c. voltage 3.The flow of electronsd .ohm 4.the unit of resistance e. Ohms Law 5.The unit in

18、 which current is measured3.Fill in the missing words according to the text.a. One ampere of current is defined as the movement of coulomb past any point of a conductor during second of time. b. One milliampere is equivalent to (0.001)of an ampere，and one microampere is equivalent to (0.000001)of an

19、 ampere.c. One volt is defined as that magnitude of electromotive force required cause a current of one to pass through a conductor having a of one ohm.d. One ohm is defined as that amount of that will limit the current in a conductor is one ampere when the applied to the conductor is one volt.4.Tra

20、nslate the following paragraph into Chinese. Potential The unit for potential difference, or electromotive force, is the volt. The abbreviation, or symbol, for this unit is V. Voltage is expressed in volts. Recall that one volt equals the amount of electromotive force (emf) that moves a current of o

21、ne ampere through a resistance of one ohm. Current The unit of measure for current flow is the ampere. The abbreviation, or symbol, for this basic unit of measure is A. Remember that one ampere equals an electron flow of one coulomb per second past a given point. Resistance Resistance is another ele

22、ctrical parameter that two letter： “R” represents the general term resistance and the Greek letter omega () represents the unit of resistance, the ohm. Remember that one ohm equals the resistance that limits the current to one ampere with one volt applied. Conductance Another electrical parameter is

23、 conductance. Conductance is the opposite of resistance. The unit of conductance is the siemens (S) named after the scientist Ernst Siemens. The abbreviation for the general term conductance is G.5.Translate the following sentences into English.电压的单位是伏特，用符号V表示。 电流的单位是安培，用符号A表示。 1伏特的电压施加在导体上产生了1安培的电流，此时电阻为1欧姆。 欧姆定律表示了电流、电压、电阻之间的关系。 End