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1、西交专业英语在线作业Resistorsare()elements.A.passiveB.activeC.independentsourcesD.dependentsources正确答案:AAnelectricheaterdraws10Afroma120Vline.Theresistanceoftheheateris().A.1200?B.120?C.12?D.1.2?正确答案:CThealgebraicsumofallvoltagesaroundaloopis().A.zeroB.indefinitevalueC.sumofvoltagerisesD.sumofvoltagedrops正确答案
2、:AON-OFFinformationcanberepresentedby()signal.A.adigitalB.ananalogC.adiscreteD.acontrol正确答案:ATheprocessquantizingthecontinuousvaluesintoabinaryscaleiscalled().A.digital-to-analogconversionB.digital-to-digitalconversionC.analog-to-digitalconversionD.analog-to-analogconversion正确答案:CThewideapplicationo
3、foperationalamplifiersliesinadvantageofusing().A.positivefeedbacknetworksB.largeopen-circuitgainC.negativefeedbacknetworksD.smalloutputimpedance正确答案:CWhenaninductionmotorwith10polesissuppliedby50Hzthree-phaseacpowersource,thesynchronousrevolutionsperminuteis().(Synchronousr/min=120f/p)A.1000B.900C.7
4、00D.600正确答案:DTheelectricmachinethatoperatesatspeedsabovesynchronousspeedworksin()region.A.motoringB.generatingC.pluggingD.stopping正确答案:BAtransformerisadevicethatcanconvertoneacvoltagetoanotheracvoltagethroughtheactionof().A.anelectriccircuitB.amagneticfieldC.anelectricfieldD.acouplingcircuit正确答案:BTh
5、eprimarywindingisconnectedto().A.thepowersourceB.theloadC.themeasurementinstrumentD.themotor正确答案:ACopperlossesare()lossesintheprimaryandsecondarywindingsofthetransformercore.A.inductiveB.capacitiveC.resistiveD.reactive正确答案:C()canprovideanasynchronouslinkbetweentwoacelectricpowersystemwithdifferentno
6、minalfrequencies.A.TheHVDC(highvoltageDC)transmissionB.TheEHV(extra-highvoltage)ACtransmissionC.TheACdistributionD.Generators正确答案:AThegeneratorvoltagesareusuallysteppeduptothetransmissionvoltagelevelby().A.seriescapacitorB.parallelreactorsC.step-uptransformersD.step-downtransformers正确答案:CTheobjectiv
7、eoftheoptimaleconomicoperationofpowersystemsis().A.tominimizethetotalproductioncostB.tomaintainfrequencyconstantC.tomaintainvoltagesconstantD.toensurebalancebetweengenerationandload正确答案:AAnyprotectionschemeconsistsbasicallyof().A.twoelementsB.threeelementsC.fourelementsD.fiveelements正确答案:ATheprotect
8、iveschemethatsenseszerosequencecurrentandoperatesasnecessaryiscalledas().A.overcurrentprotectionB.zerosequenceprotectionC.negativesequenceprotectionD.directionalprotection正确答案:BThedistanceprotectionisappliedtoprotect().A.transformersB.generatorsC.transmissionlinesD.buses正确答案:CThethermalenergyofthest
9、eamisconvertedinto()energybytheturbine.A.electricalB.mechanicalC.chemicalD.potential正确答案:B()isusedascoolantinlight-waterreactors.A.GasB.OrganiccompoundC.MoltensaltD.Water正确答案:DIntheformof()theoutputiscontinuouslyfedbackandcomparedwiththereferenceinput.A.continuouscontrolB.discontinuouscontrolC.discr
10、ete-datacontrolD.sampled-datacontrol正确答案:ATheoveralltransferfunctionistheratioofthetransformofthecontrolledvariabletothetransformof().A.thecontrolledvariableB.thereferenceinputC.thefeedbackD.theoutputvariable正确答案:BThesystemscharacteristicequationcanbeusedtodetermine()ofalineartime-invariantsystem.A.
11、thestabilityB.magnitudeofthesteady-stateerrorC.thecontrollabilityD.theobservability正确答案:AIntheroot-locusmethodtheactualtimeresponseofasystemcanbeobtainedbymeansof().A.theinverseFouriertransformB.theinverseLaplacetransformC.theFouriertransformD.theLaplacetransform正确答案:BTheBuck(降压式变换器)isa()converter.A
12、.voltagestep-upB.currentstep-downC.currentstep-upD.resistance正确答案:CMostdesktopcomputersuseaseparate()asadisplaydevice,wherenotebookcomputersuseaflatpanelLCDscreen(liquidcrystaldisplayscreen)thatattachedtothesystemunit.A.keyboardB.MouseC.MonitorD.harddisk正确答案:CAdesktopcomputerssoundcardsendssignalsto
13、external().A.printerB.speakerC.ModemD.keyboard正确答案:BDatastoredinRAM()whenthepowerofthecomputeristurnedoff.A.isheldpermanentlyB.permanentlydisappearsC.isheldtemporarilyD.temporarilydisappears正确答案:BThenotebookcomputersuse()asstandarddisplayequipment.A.CRTdisplayB.LCDsC.LEDD.TVscreen正确答案:BImageclarityo
14、nacomputerscreenismeasuredwith().A.screensizeB.dotpitchC.resolutionD.colordepth正确答案:B()thatconnectsatleasttwonetworksmakesdecisionaboutthebestroutefordata.A.AmodemB.AnetworkcardC.AhubD.Arouter（路由器）正确答案:D#thedirectcurrentisuseful,ithasonegreat#,thatis,thereisnoeasy,economicalwaytoincreaseordecreaseits#.Thealternatingcurrenthasnotthisdisadvantage.#aspecialdevice,itis#totransformahighvoltageintoa#voltageoralowvoltageintoahighvoltage.The#thatweusetotransformthevoltageiscalleda#.Thealternatingcurrentcan#bechangedeasilyintothedirectcurrent.Thede
