2019年秋西交《专业英语》在线作业答案.pdf

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1、西交专业英语在线作业试卷总分:100得分:100一、单选题(共 30 道试题,共 60 分)1.Resistors are()elements.A.passiveB.activeC.independent sourcesD.dependent sources仔细分析以上试题，并作出正确选择正确答案是:A2.An electric heater draws 10 A from a 120V line.The resistance of the heater is().A.1200?B.120?C.12?D.1.2?仔细分析以上试题，并作出正确选择正确答案是:C3.The algebraic su

2、m of all voltages around a loop is().A.zeroB.indefinite valueC.sum of voltage risesD.sum of voltage drops仔细分析以上试题，并作出正确选择正确答案是:A4.ON-OFF information can be represented by()signal.A.a digitalB.an analogC.a discreteD.a control仔细分析以上试题，并作出正确选择正确答案是:A5.The process quantizing the continuous values into a

3、 binary scale is called().A.digital-to-analog conversionB.digital-to-digital conversionC.analog-to-digital conversionD.analog-to-analog conversion仔细分析以上试题，并作出正确选择正确答案是:C6.The wide application of operational amplifiers lies in advantage of using().A.positive feedback networksB.large open-circuit gain

4、C.negative feedback networksD.small output impedance仔细分析以上试题，并作出正确选择正确答案是:C7.When an induction motor with 10 poles is supplied by 50Hz three-phase ac power source,the synchronous revolutions per minute is().(Synchronous r/min=120 f/p)A.1000B.900C.700D.600仔细分析以上试题，并作出正确选择正确答案是:D8.The electric machine

5、 that operatesat speeds abovesynchronous speed works in()region.A.motoringB.generatingC.pluggingD.stopping仔细分析以上试题，并作出正确选择正确答案是:B9.A transformer is a device that can convert one ac voltage to another ac voltagethrough the action of().A.an electric circuitB.a magnetic fieldC.an electric fieldD.a coup

6、ling circuit仔细分析以上试题，并作出正确选择正确答案是:B10.The primary winding is connected to().A.the power sourceB.the loadC.the measurement instrumentD.the motor仔细分析以上试题，并作出正确选择正确答案是:A11.Copper losses are()losses in the primary and secondary windings of thetransformer core.A.inductiveB.capacitiveC.resistiveD.reactive

7、仔细分析以上试题，并作出正确选择正确答案是:C12.()can provide an asynchronous link between two ac electric power system withdifferent nominal frequencies.A.The HVDC(high voltage DC)transmissionB.The EHV(extra-high voltage)AC transmissionC.The AC distributionD.Generators仔细分析以上试题，并作出正确选择正确答案是:A13.The generator voltages are

8、 usually stepped up to the transmission voltage levelby().A.series capacitorB.parallel reactorsC.step-up transformersD.step-down transformers仔细分析以上试题，并作出正确选择正确答案是:C14.The objective of the optimal economic operation of power systems is().A.to minimize the total production costB.to maintain frequency

9、constantC.to maintain voltages constantD.to ensure balance between generation and load仔细分析以上试题，并作出正确选择正确答案是:A15.Any protection scheme consists basically of().A.two elementsB.three elementsC.four elementsD.five elements仔细分析以上试题，并作出正确选择正确答案是:A16.The protective scheme that senses zero sequence current

10、and operates as necessaryis called as().A.overcurrent protectionB.zero sequence protectionC.negative sequence protectionD.directional protection仔细分析以上试题，并作出正确选择正确答案是:B17.The distance protection is applied to protect().A.transformersB.generatorsC.transmission linesD.buses仔细分析以上试题，并作出正确选择正确答案是:C18.The

11、 thermal energy of the steam is converted into()energy by the turbine.A.electricalB.mechanicalC.chemicalD.potential仔细分析以上试题，并作出正确选择正确答案是:B19.()is used as coolant in light-water reactors.A.GasB.Organic compoundC.Molten saltD.Water仔细分析以上试题，并作出正确选择正确答案是:D20.In the form of()the output is continuously fe

12、d back and compared with thereference input.A.continuous controlB.discontinuous controlC.discrete-data controlD.sampled-data control仔细分析以上试题，并作出正确选择正确答案是:A21.The overall transfer function is the ratio of the transform of the controlledvariable to the transform of().A.the controlled variableB.the ref

13、erence inputC.the feedbackD.the output variable仔细分析以上试题，并作出正确选择正确答案是:B22.The systems characteristic equation can be used to determine()of a lineartime-invariant system.A.the stabilityB.magnitude of the steady-state errorC.the controllabilityD.the observability仔细分析以上试题，并作出正确选择正确答案是:A23.In the root-lo

14、cus method the actual time response of a system can be obtained bymeans of().A.the inverse Fourier transformB.the inverse Laplace transformC.the Fourier transformD.the Laplace transform仔细分析以上试题，并作出正确选择正确答案是:B24.The Buck(降压式变换器)is a()converter.A.voltage step-upB.current step-downC.current step-upD.re

15、sistance仔细分析以上试题，并作出正确选择正确答案是:C25.Most desktop computers use a separate()as a display device,where notebookcomputers use a flat panel LCD screen(liquid crystal display screen)that attachedto the system unit.A.keyboardB.MouseC.MonitorD.hard disk仔细分析以上试题，并作出正确选择正确答案是:C26.A desktop computers sound card

16、 sends signals to external().A.printerB.speakerC.ModemD.keyboard仔细分析以上试题，并作出正确选择正确答案是:B27.Data stored in RAM()when the power of the computer is turned off.A.is held permanentlyB.permanently disappearsC.is held temporarilyD.temporarily disappears仔细分析以上试题，并作出正确选择正确答案是:B28.The notebook computers use()a

17、s standard display equipment.A.CRT displayB.LCDsC.LEDD.TV screen仔细分析以上试题，并作出正确选择正确答案是:B29.Image clarity on a computer screen is measured with().A.screen sizeB.dot pitchC.resolutionD.color depth仔细分析以上试题，并作出正确选择正确答案是:B30.()that connects at least two networks makes decision about the best route fordata

18、.A.A modemB.A network cardC.A hubD.A router（路由器）仔细分析以上试题，并作出正确选择正确答案是:D二、完型填空(共 2 道试题,共 40 分)1.#the direct current is useful,it has one great#,that is,there is no easy,economical way to increase or decrease its#.The alternating current has not thisdisadvantage.#a special device,it is#to transform a

19、high voltage into a#voltageor a low voltage into a high voltage.The#that we use to transform the voltage iscalled a#.The alternating current can#be changed easily into the direct current.The device which can do this is spoken of as a#.(1).A.AlsoB.AlthoughC.AsD.For(2).A.meaningB.thingC.advantageD.dis

20、advantage(3).A.resistanceB.capacitanceC.voltageD.current(4).A.MakingB.MarkingC.UsingD.Having(5).A.possibleB.impossibleC.easyD.different(6).A.highB.lowC.largeD.small(7).A.thingB.machineC.oneD.device(8).A.transferB.transformerC.changeD.charge(9).A.alsoB.easilyC.hardD.but(10).A.receiverB.remoteC.rectif

21、ierD.refiner仔细分析以上试题，并作出正确选择正确答案是:(1).B(2).D(3).C(4).C(5).A(6).B(7).D(8).B(9).A(10).C2.There are#inds of current:direct current(DC)and alternating#(AC).A directcurrent is a current flowing in a#always in one direction.#alternating current isacurrent#changingitsdirectionofflow.Theelectriccurrent#thro

22、ughelectric#lines is#current.This is because AC is easy to#and more economical whenwe transmit it over long#.(1).A.oneB.twoC.threeD.four(2).A.conductorB.coincidenceC.currentD.currency(3).A.currentB.currencyC.semiconductorD.conductor(4).A.AB.AnC.TheD.That(5).A.probablyB.periodicallyC.timelyD.second(6).A.transmittedB.transportedC.transformedD.unlighted(7).A.powderB.energyC.pouredD.power(8).A.alternativeB.alwaysC.alternatingD.alter(9).A.considerB.consoleC.controlD.consent(10).A.timeB.distancesC.wayD.ago仔细分析以上试题，并作出正确选择正确答案是:(1).B(2).C(3).D(4).B(5).B(6).A(7).D(8).C(9).C(10).B