雨课堂学堂在线学堂云《Circuits and Electrical Skills（宁波城市职业技术学院）》单元测试考核答案

第1题Whichofthefollowingpracticesisunsafewhenusinghouseholdappliances____?ACheckthepowerplug,wiresandappliancesfordamagebeforeuseBTouchtheswitchorplugofanappliancewithwethandsCAvoidsharingapoweroutletwithmultiplehigh-powerelectricalappliancestopreventoverloadingDDonothangclothesonwiresandkeeptheareaaroundtheappliancewellventilated第2题Whichofthefollowingstatementsiswrong:____?AThehumanbodyisaconductor.Whenthehumanbodybecomespartofaclosedcircuit,currentwillflowthroughit,whichmaycauseelectricshockBHangingwetclothesonthewiretomakefulluseofthespaceCElectricshockaccidentsinhouseholdcircuitsareusuallycausedbydirectorindirectconnectionbetweenthehumanbodyandthelineDThereisoftenawarningsign"Highvoltagedanger,donotapproach"abovethehigh-voltagetransmissionline,andweshouldstayawayfromhigh-voltageequipment第3题Whichofthefollowingpracticesisnecessarywhenperforminghomecircuitrepairs____?AYoucanreplacethelightbulbdirectlywithoutturningoffthepowerBYoucantouchtheexposedpartofthewirewithyourbarehandwithoutanyprotectivemeasuresCYoucanwipetheworkingelectricalapplianceswithadampclothDBeforerepair,turnoffthepowerswitchanduseavoltagetestertotestwhetherthecircuitisenergized第1题Whensomeoneiselectricshocked,thecorrectmeasuretotakefirstis:____?AQuicklyturnoffthepowersupplyoruseaninsulatingobjecttoseparatethepatientfromthepowersupplyBPullthepersonawaywithbarehandsfromthepowersupplyimmediatelyCCalltheemergencynumberandwaitforprofessionalrescueimmediatelyDPerformCPRonthepatientfirst,thendealwiththepowersupplyproblem第2题Foradministeringfirstaidtothepatient,thecorrectmethodtodetermineifthepatientisconsciousis:____?APatthepatient’sshouldergentlyandcallhisnameloudlyBDirectlycheckthepatient’spupiloftheeyesCTouchtheskinofthepatienttofeelhisbodytemperatureDObservewhetherthepersonhasspontaneousbreathing第3题Whichofthefollowingpracticesisincorrectwhenperformingfirstaidforelectricshock____?AIfthepatientstopsbreathingbutstillhasaheartbeat,artificialrespirationshouldbeperformedimmediatelyBIfthepatient’sheartstopsbeatingbutstillhasbreath,CPRshouldbeperformedimmediatelyCWhenadministeringfirstaidtothepatient,artificialrespirationandCPRcanbeperformedatthesametimeDAfterthepatientisdisconnectedfromthepowersource,heshouldbemoveddirectlytoadryandventilatedplacetoavoidelectricshockagain.2.1Circuitsandcircuitmodels第1题Incircuittheory,anidealcircuitelementrefersto:____?AAnactualelementwithfixedelectricalcharacteristicsBAnabstractconceptusedtodescribecircuitbehaviorwithoutconsideringthecomplexstructureandenergylossinsidetheelementCAnelementthatcanonlyworkproperlyundercertainconditionsDAnelementwhoseparameterscanonlybedeterminedthroughexperimentalmeasurement第2题Whichofthefollowingisnotabasiccomponentofacircuit____?APowersupply,adevicethatprovideselectricalenergyBLoad,adevicethatconsumeselectricalenergyCWire,ametalwirethatconnectsthepowersupplyandtheloadDElectromagneticwaves,amediumfortransmittinginformation第3题Incircuitanalysis,themainadvantageofusingcircuitmodelsis:____?ABeingabletofullysimulateallphysicalphenomenainactualcircuitsBSimplifycomplexcircuitsforeasierunderstandingandcalculationCPredictthelifeandreliabilityofcircuitcomponentsDAccuratelymeasuretheresistancevalueofeachcomponentinthecircuit2.2Physicalquantitiesinelectricalcircuits第1题Inacircuit,thephysicalquantitythatindicatesthemagnitudeofthecurrentis:____?AVoltageBResistanceCCurrentDPower第2题Inaclosedcircuit,thefunctionofvoltageis:____?AConsumeelectricalenergyBGenerateelectricalenergyCDrivethedirectionalmovementofchargestocreatecurrentDPreventcurrentfrompassing第3题Regardingtheelectricalpowerinthecircuit,whichofthefollowingstatementsiscorrect:____?AElectricalpowerisaphysicalquantitythatdescribeshowfastthecurrentdoesworkBThegreatertheelectricalpower,themoreelectricalenergyisconsumedCElectricalpowerisnotrelatedtovoltageandcurrentDInthesamecircuit,thegreatertheresistanceofthecomponent,thegreatertheelectricalpower2.3Basiclawandoperatingstatesofelectriccircuits第1题RegardingtheOhm’slaw,whichofthefollowingisincorrect:____?AInametalconductor,thecurrentisproportionaltothevoltageacrosstheconductorBTheexpressionofOhm'slawisI=U/R,whereI,U,andRrepresentcurrent,voltage,andresistancerespectivelyCInametalconductor,thecurrentisinverselyproportionaltotheresistanceoftheconductorDOhm'slawappliestoallcircuits第2题Whichofthefollowingsituationswillcauseexcessivecurrentinthecircuit,whichmaycausefireorequipmentdamage____?AThecircuitisinanopencircuitstateBTheloadinthecircuitistoolargeCThecircuitisshort-circuitedDTheresistanceinthecircuitincreases第3题Inacircuit,ifthepowersupply,switch,wiresandelectricalappliancesareallconnectedproperlyandtheswitchisclosed,thecircuitisin:____?AClosecircuitstate,andcurrentcanflowBOpencircuitstate,andcurrentcannotflowCShortcircuitstate,andcurrentistoolargeDUnabletodetermine,currentmeasurementisrequired2.4Kirchhoff'sLaw第1题WhichofthefollowingstatementscorrectlydescribesKirchhoff’sCurrentLawinacircuit____?AThesumofthecurrentflowingintoanynodeisequaltothesumofthecurrentflowingoutthatnodeBThesumofthevoltagedropsinanyloopisequaltothesumofthevoltagerisesCResistanceisinverselyproportionaltocurrent,andvoltageisdirectlyproportionaltocurrentDCurrentisproportionaltothepowersourceelectromotiveforceandinverselyproportionaltoresistance第2题WhenapplyingKirchhoff'sVoltageLawtoanalyzeaclosedloopcontainingmultiplepowersuppliesandloads,whichofthefollowingstatementsiscorrect?____?AThedirectionofthevoltagedropandvoltageriseintheloopcanbechosenarbitrarilyBThesumofthevoltagedropsonallcomponentsintheloopmustbezeroCThesumofthevoltagerisesprovidedbythepowersuppliesintheloopmustbezeroDThesumofthevoltagedropsonallcomponentsintheloopmustbeequaltothesumofthevoltagerisesprovidedbyallpowersupplies第3题Inacomplexcircuitwithmultiplepowersuppliesandloads,inordertoanalyzethecurrentineachbranch,wemainlyapply:____?AKirchhoff'sCurrentLawBKirchhoff'sVoltageLawCBothDNeither,thereareothersimplermethods2.5Equivalenttransformationofvoltageandcurrentsources第1题Incircuitanalysis,whenperformingequivalenttransformationbetweenvoltagesourceandcurrentsource,thecircuitbeforeandafterthetransformationmustmaintain:____?AThecurrentmagnituderemainsunchangedBThevoltagemagnituderemainsunchangedCTheexternalequivalenceremainsunchangedDTheinternalstructureremainsunchanged第2题Theactualvoltagesourceconsistsofaconstantvoltagesourcein()withaninternalresistance,whiletheactualcurrentsourceconsistsofaconstantcurrentsourcein()withaninternalresistance.____?ASeries,ParallelBSeries,SeriesCParallel,SeriesDParallel,Parallel第3题Cananidealvoltagesource(withoutinternalresistance)andanidealcurrentsource(withoutinternalresistance)beequivalentlytransformed?____?AYes,becausetheyareidealcomponentsBNo,becausetheircharacteristicsarecompletelydifferentCYes,butadditionalcomponentsneedtobeintroducedDDependsonthespecificconnectionmethodofthecircuit3.1Basicconceptsofsinusoidalalternatingcurrent第1题Thethreeelementsofsinusoidalalternatingcurrentare:____?AFrequency,phase,periodBInstantaneousvalue,frequency,initialphaseCRMSvalue,frequency,initialphaseDMaximumvalue,period,angularfrequency第2题Givenasinusoidalalternatingcurrenti= 5sin(314t+250),thentheinitialphaseis:____?A25°B65°C15°D35°第3题TheperiodandfrequencyofutilityfrequencyalternatingcurrentusedinChina’sindustrialandagriculturalproductionanddailylifeare:____?A0.02s,50HzB0.2s,50HzC0.02s,60HzD5s,60Hz3.2Phasorrepresentationofsinusoidalquantities第1题WhenthesinusoidalvoltageVisrepresentedbytheamplitude(maximumvalue)phasor,itcanbewrittenas:____?ABCD第2题Whichofthefollowingstatementsiscorrect:____?ASinusoidalquantitiescanberepresentedbyphasors,sophasorsareequaltosinusoidalquantities.BThesumanddifferenceofsinusoidalquantitiesofdifferentfrequenciescanbecalculatedbyphasordiagramanalysis.COnlysinusoidalquantitiesofthesamefrequencycanbedrawnonthesamephasordiagram.DThedifferencebetweentheinitialphasesoftwosinusoidalquantitiesisthephasedifferencebetweenthem.3.3ACcircuitswithresistivecomponents第1题Inapurelyresistivecircuit,therelationshipbetweenvoltageandcurrentis:____?AVoltageexceedscurrentby90degreesBCurrentexceedsvoltageby90degreesCVoltageandcurrentarein-phaseDThephaserelationshipbetweenvoltageandcurrentisuncertain第2题Whenaresistorwitharesistanceof10ΩisconnectedtoanACpowersupply,andthecurrentinthecircuitis100mAasmeasuredbyamultimeter,thepowerconsumedbytheresistoris:____?A0.5WB0.1WC0.2WD1W第3题Theinstantaneouspowerontheresistorelementisalwaysgreaterthanzero,whichmeansthattheresistorisa()element.____?APowersupplyBEnergystorageCEnergyconsumptionDNon-energyconsumption3.4ACcircuitswithinductivecomponents第1题Inapureinductivecircuit,().____?AVoltageandcurrenthavethesamefrequency,andthevoltageandcurrentarein-phaseBVoltageandcurrenthavethesamefrequency,andthevoltagephaseexceedsthecurrentby90degreesCVoltageandcurrenthavethesamefrequency,andthevoltagephaseisoppositetothecurrentDVoltageandcurrenthavethesamefrequency,andthevoltagephaselagsthecurrentby90degrees第2题InaDCsteady-statecircuit,inductanceisequivalentto()state.____?AShortcircuitBOpencircuitCResistanceDBrokencircuit第3题Whenasinusoidalvoltageu= 10sin(314t+30∘)VsappliedtoaninductiveelementwithaninductivereactanceXL= 5Ω,theRMSvalueofthecurrentpassingthroughtheelementis:____?A2B2C5D103.5ACcircuitswithcapacitivecomponents第1题Inapurecapacitivecircuit,().____?AVoltageandcurrenthavethesamefrequency,andthevoltageandcurrentareinphaseBVoltageandcurrenthavethesamefrequency,andthevoltagephaseexceedsthecurrentby90degreesCVoltageandcurrenthavethesamefrequency,andthevoltagephaseisoppositetothecurrentDVoltageandcurrenthavethesamefrequency,andthevoltagephaselagsthecurrentby90degrees第2题Whenasinusoidalvoltageu= 10sin(314t+30∘)VisappliedtoaninductiveelementwithcapacitivereactanceXC= 5Ω,thenthecurrentIpassingthroughtheelementis().____?A2sin(314t+120∘)AB2sin(314t+90∘)AC2sin(314t−60∘)AD2sin(314t+30∘)A第3题CapacitivereactanceXCisafunctionoffrequencywhenCisconstant.Thehigherfis,the()XCis.____?AGreaterBSmallerCUncertainDUnchanged3.6RLCseriesACcircuit第1题IntheRLCseriesACcircuit,().____?AWhenXL>XCinthecircuit,thecircuitisgenerallyinductivetotheoutsideBWhenXL>XCinthecircuit,thecircuitisgenerallycapacitivetotheoutsideCWhenXLDWhenXL=XCinthecircuit,theoverallexternalcharacteristicofthecircuitisuncertain第2题TheapparentpowerofacomponentisS=1000VAandthepowerfactoris0.5,Whatareitsactivepowerandreactivepower?____?AP=500W,Q=500VarBP=866W,Q=866VarCP=500W,Q=1000VarDP=500W,Q=866Var第3题InaRLCseriescircuit,whichofthefollowingformulasisincorrect?____?Au=uR+uL+uCBU=UR+UL+UCCD3.7Improvementofpowerfactor第1题Thegeneralmethodtoimprovethepowerfactorofaninductivecircuitisto()atbothendsoftheinductivecircuit.____?AConnectacapacitorinseriesBConnectaninductorinseriesCConnectacapacitorinparallelDConnectaninductorinparallel第2题Whichofthefollowingstatementsisincorrect?____?AInordertoimprovetheutilizationefficiencyofpowergenerationequipment,reducepowerloss,andimproveeconomicbenefits,thepowerfactorofthecircuitmustbeimproved.BLowpowerfactorleadstotheinabilitytofullyutilizethepowercapacityandincreasesenergywasteinthepowersupplyanddistributionlines.CThegeneralmethodtoimprovethepowerfactoristoconnectcapacitorsinparallelintheinductivecircuit.DThepracticalmeaningofimprovingthepowerfactoris:(1)toimprovetheenergyutilizationefficiencyofthepowersupplyequipmentitself;(2)toincreasetheenergylossonthetransmissionline.4.1Basicknowledgeofthree-phasepowersupply第1题Thecorrectstatementaboutthethree-phasesymmetricalelectromotiveforceis:()____?ATheyreachtheirmaximumvalueatthesametimeBTheirmaximumvalueandfrequencyarethesame,andthephasedifferenceis120degreesCTheirperiodandphasearethesameDBecausetheyareindifferentspatialpositions,theirmaximumvalues​​arealsodifferent第2题Whenthepowersupplyisinstarconnection,thelinevoltageis3timesthephasevoltage,and().____?AThephasevoltageisin-phasewiththelinevoltageBThelinevoltageexceedsthecorrespondingphasevoltageby30degreesCThelinevoltagelagsthecorrespondingphasevoltageby30degreesDUncertain第3题Whenthethree-phasepowersupplyisindeltaconnection,().____?AThephasevoltageisequaltothelinevoltageBThephasevoltageisgreaterthanthelinevoltageCThephaseandlinevoltagesconformtoacertainproportionalrelationshipDThephasevoltageislessthanthelinevoltage4.2Connectionofthree-phaseload第1题Whenthelightingloadisinstarconnection,wemustuse().____?AThree-phasethree-wiresystemBAnywiresystemCSingle-phasesystemDThree-phasefour-wiresystem第2题Inathree-phasefour-wirecircuit,thefunctionoftheneutrallineisto().____?AEnsurethatthephasevoltageontheloadissymmetricalBEnsurethatthelinevoltageoftheloadisequalCEnsurethatthelinecurrentoftheloadisequalDEnsurethatthephasecurrentoftheloadisequal第3题Whenathree-phasesymmetricalloadisindeltaconnection,whichofthefollowingstatementsiscorrectabouttherelationshipbetweenlinecurrentandphasecurrent().____?ALinecurrentisequaltophasecurrentBLinecurrentislessthanphasecurrentCLinecurrentis3timesthephasecurrentandexceedsthecorrespondingphasecurrentby30degreesDLinecurrentis3timesthephasecurrentandlagsthecorrespondingphasecurrentby30degrees4.3Powerofthethree-phasecircuit第1题Forathree-phasecircuit,whentheloadissymmetrical,theactivepowerofeachphaseis().____?ANotequalBEqualtothethree-phasepowerCEqualDUncertain第2题Regardlessofwhethertheloadisindeltaorstarconnection,thetotalactivepowermustbeequaltothe()ofactivepowersofeachphase.____?ASumBDifferenceCProductDUncertain第3题Reactivepowerofsymmetricalthree-phaseloadisQ=3UlIlsin⁡φ,wheretheangleφis().____?AThephasedifferencebetweenthelinevoltageandthelinecurrentBThephasedifferencebetweenthelinevoltageandthephasecurrentCThephasedifferencebetweenthephasevoltageandthephasecurrentDUncertain4.4Three-phaseACasynchronousmotor第1题Thepurposeofchangingthepowerphasesequenceofathree-phaseasynchronousmotoristomakethemotor____?.AChangeitsdirectionofrotationBChangeitsspeedCChangeitspowerDReduceitsvoltagetostart第2题Whentheslipratioofathree-phaseasynchronousmotoriss=1,itsrotationalspeedis____?.ARatedspeedBSynchronousspeedCZeroDMaximumspeed第3题Inathree-phaseasynchronousmotor,thespeedoftherotatingmagneticfielddependson____?.ARotorrotationalspeedBFrequencyofthepowersupplyvoltagef1CPolenumberofthestatorwindingpDRatiooff1top5.1Magneticfieldanditsbasicphysicalquantities第1题Whichofthefollowingstatementsiscorrectaboutthemagneticfieldline?____?AMagneticfieldlinesarerealphysicallinesthatcanbedirectlyobservedthroughexperiments.BMagneticfieldlinesstartfromtheNpoleofthemagnet,entertheSpole,andformaclosedloopinsidethemagnet.CThedensityofmagneticfieldlinesindicatesthestrengthofthemagneticfield,butthedirectionofmagneticfieldlinescannotindicatethedirectionof