雨课堂学堂在线学堂云《Electromagnetism( 西交)》单元测试考核答案

注：不含主观题第1题单选题(1分)Whatistheratioofelectrostaticrepulsionandgravitationalattractionbetweentwoelectrons?()Given:ABCD第2题单选题(1分)Theelectricfieldintensityatapointsituated4mfromapointchargeis200N/C.Ifthedistanceisreducedto2m,thefieldintensitywillbe()A400N/CB600N/CC800N/CD1200N/C第3题单选题(1分)IftheelectricfluxΦepassingthroughtheclosedsurfaceSiszero,thenitiscertain()AThereisnochargeinthesurfaceSBThereisnonetchargeinsurfaceSCThefieldstrengthateachpointonthesurfaceSisequaltozeroDThefieldstrengthateachpointonthesurfaceSisnotequaltozero第4题单选题(1分)FiveequalpointchargesofQ=

C,areplacedatx=2,3,4,5and6cm.Theelectricpotentialatoriginwillbe()A416VB128VC325VD261V第5题单选题(1分)Thefluxandpotentialfunctionsduetoalinechargeandduetotwoconcentriccircularconductorsareofthefollowingform()AConcentriccircularequipotentiallinesandstraightradialfluxlinesBConcentriccircularfluxlinesandstraightequipotentiallinesCEquipotentialsduetolinechargeareconcentriccylindersandequipotentialsduetotwoconductorsarestraightlinesDEquipotentialsduetolinechargearestraightflatsurfacesandthoseduetotwoconductorsareconcentriccylinders第6题判断题(1分)Thedirectionoftheelectricfieldstrengthisthesameasthedirectionoftheelectricfieldforceexperiencedbythepositivetestchargeatthatpoint.()第7题判断题(1分)Thedensertheelectricfieldlines,thegreatertheelectricfieldstrengthatthatlocation.()ch2-Exercises第1题单选题(1分)AU1BU2CU1+U2DU1-U2第2题单选题(1分)Forwhichofthefollowingparametervariation,thecapacitanceofthecapacitorremainsunaffected?()ADistancebetweenplatesBAreaoftheplatesCNatureofdielectricDThicknessoftheplates第3题单选题(1分)Thepotentialgradientacrossthematerialoflowpermittivityisthanacrossthematerialofhighpermittivity.()AsmallerBgreaterCbothAandBDnoneoftheabove第4题判断题(1分)Thethinnerthedielectric,themorethecapacitanceandthelowerthevoltagebreakdownratingforacapacitor.()第5题判断题(1分)Acapacitorcanstorechargebecauseithasadielectricbetweentwoconductors.()第6题判断题(1分)Thecurrentinthedischargingcapacitorgrowslinearly.()第7题判断题(1分)Thecurrentinthedischargingcapacitorgrowsexponentially.()

ch3-Exercises第1题单选题(1分)Twopositivechargesq1andq2aremovingtotherightinthefigure.Whatitthedirectionoftheforceonchargeq1duetothemagneticfieldproducedbyq2?AIntothepageBOutofthepageCUpthepageDDownthepage第2题单选题(1分)Twopositivechargesq1andq2aremovingtotherightinthefigure.Whatisthedirectionoftheforceonchargeq2duetothemagneticfieldproducedbyq1?AIntothepageBOutofthepageCUpthepageDDownthepage第3题单选题(1分)Thenegativelychargeddiskinthefigureisrotatedclockwise.WhatisthedirectionofthemagneticfieldatpointAintheplaneofthedisk?AIntothepageBOutofthepageCUpthepage

DDownthepage第4题单选题(1分)ABCD第5题单选题(1分)AB(z)isconstant.BCD第6题单选题(1分)ABCD第7题单选题(1分)AItisareasonableapproximationforcrosssectionsclosetocircles.B

Itisareasonableapproximationforanycross-sectionalshape.CItistrueforcross-sectionalshapesofsufficientsymmetry(suchasequilateralanglesorsquares).DItistrueforanycross-sectionalshape.第8题单选题(1分)Canastaticmagneticfielddopositiveworkonachargedparticle?AYesBYes,butonlyiftheparticlehasapositivechargeCYes,butonlyiftheparticlehasaninitialvelocityDNo第9题单选题(1分)

Inwhichdirectioncouldtheelectronbemoving?ANorthBSouthCUpDDown第10题单选题(1分)ANorthBSouthCUpDDown第11题单选题(1分)ThemagneticfieldinFig.pointsintothepage.Asmallmetalplanemovesdownthepage.Accordingtothepilot,whichwingbecomesnegativelychargedwhiletheplaneismoving?ATheleftwingBTherightwingCNeitherwingbecomescharged.DTheanswerdependsonthesignofthechargecarriersintheplane.第12题单选题(1分)ThemagneticfieldinFig.pointsintothepage.Asmallmetalplanemovesdownthepage.

Theplaneisnowturnedaroundand“flies”tothetopofthepage.Whichwingnowbecomesnegativelychargedwhiletheplanemovesupthepage?ATheleftwingBTherightwingCNeitherwingbecomescharged.DTheanswerdependsonthesignofthechargecarriersintheplane.第13题单选题(1分)Thefigureshowsseveralwiresegmentsthatcarryequalcurrentsfromatob.Thewiresareinauniformmagneticfielddirectedintothepage.Whichwiresegmentexperiencesthelargestnetforce?A1B2C3DAllexperiencethesamenetforce.EThequestioncannotbeansweredwithoutadditionalinformation.第14题多选题(2分)WhichofthefollowingpropertiesofaprotoncanchangewhileitmovesfreelyinauniformmagneticfieldB?(Theremaybemorethanonecorrectanswer.)AMassBSpeedCVelocityDMomentumEKineticenergy正确答案：CDch4-Exercises第1题单选题(1分)Amagneticdipoleisinanonuniformmagneticfield.Thedipolewill.Aalwaysbeattractedtotheregionwithastrongermagneticheld.Balwaysberepelledfromtheregionwithastrongermagneticfield.Cmightberepelled,butwilleventuallyflipoverandbeattractedtotheregionwithastrongermagneticfield.Dmightbeattracted,butcouldflipoverandthenberepelledfromtheregionwithastrongermagneticfield.第2题单选题(1分)Whichofthefollowingdoesnotsignificantlycontributetothemagneticpropertiesofasubstance?AOrbitalmagneticmomentsofelectronsBSpinmagneticmomentsofelectronsCMagneticmomentsofprotonsandneutronsDAllcontributeequally.第3题单选题(1分)Whatareunitsforthemagnetization?ATBCC/m·sDC·m/s第4题单选题(1分)Whichtypeofsubstancehasthelargestatomicdipolemoments?AParamagneticBDiamagneticCFerromagneticDParamagneticandferromagneticsubstancestendtobeaboutthesame,whereasdiamagneticsubstanceshavenopermanentmagneticmoment.EAllthreetypesareaboutthesame.第5题单选题(1分)Asmall,cylindricalbarmagnethasadiameterof1cm,alengthof2cm,andadipolemomentof5J/T.Assumingthemagneticfieldwereproducedbyasinglecurrentlooparoundthemagnet,abouthowlargewouldthiscurrentbe?A0.7mAB0.7AC70AD70,000A第6题单选题(1分)Fordistancesdmuchlargerthanthedimensionsofthemagneticdipoles,theforcebetweentwodipolesisproportionaltoABCD第7题单选题(1分)Ifamagneticmonopoleweretoexist,whatwouldbeappropriateunits?AWb/TBCC/m·sDC/TEThechargeofthemonopolewouldrequiretheintroductionofanewunit.ch5-Exercises第1题单选题(1分)Apermanentmagnetisdropped,southpole-down,throughaconductingloopasshown.Asthemagnetfallstowardandthenfallspasttheareaoftheloop,whatwillbethedirectionofthecurrentflow?AClockwisewhenfallingtoward,butcounterclockwiseasfallingawayBClockwisewhenfallingtoward,andclockwiseasfallingawayCCounterclockwisewhenfallingtoward,butclockwiseasfallingawayDCounterclockwisewhenfallingtoward,andcounterclockwiseasfallingawayETherewillbenocurrentinduced,becausethereisnochangingmagneticflux.第2题单选题(1分)Thelong,straightwirecarriesacurrentitotherightthatincreaseswithtime.Whatisthedirectionoftheinducedcurrentinthecircularwireloop,whichliesinaplaneperpendiculartothewire?AClockwiseasviewedfromtherightBCounterclockwiseasviewedfromtherightCThereisnoinducedcurrent.第3题单选题(1分)Thestraightwirecarriesaconstantcurrentitotherightasshown.Iftheexternalforceinsteadpullsthelooptotheleft,paralleltothewire,whatisthedirection(ifany)oftheinducedcurrentintheloop?AClockwiseBCounterclockwiseCThereisnoinducedcurrent.第4题单选题(1分)Along,straightwirecarriesacurrentthatdecreaseslinearlywithtime.Whatisthedirectionoftheinducedelectricfieldoutsidethewire?AParalleltothecurrentBOppositetothecurrentCPointingradiallyoutwardfromthewireDPointingradiallyinwardtowardthewireEThereisnoinducedelectricfieldoutsidethewire.第5题单选题(1分)Aflexibleconductingloopisintheshapeofacirclewithavariableradius.Theloopisinauniformmagneticfieldperpendiculartotheplaneoftheloop.Tosustainaconstantemf

intheloop,theradiusrmustvarywithtimeaccordingtoABCDrshouldbeconstant.第6题单选题(1分)Themagneticfieldinaregionofspaceisgivenby.Whatisthedirectionoftheinducedelectricfieldwhent=0s?AParalleltothexaxisBParalleltotheyaxisCTheelectricfieldisincirclescenteredonthexaxis.DThereisnoinducedelectricfieldwhent=0s.第7题单选题(1分)Thecurrentthroughaninfinitelylongsolenoidisincreasedlinearlyasafunctionoftime.TheelectricfieldinsidethesolenoidisAintheformofcirclescenteredontheaxisofthesolenoid.Bparalleltotheaxisofthesolenoid.Cradiallydirectedoutwardfromtheaxisofthecylinder.Dzero.第8题单选题(1分)Aloopofconductingwireintheplaneofthepage,witharadiusof0.50mandanetresistanceofR=0.5Ω,isplacedinaconstantmagneticfieldB=4.0Tdirectedintothepageasshown.Whichstatementistrue?AThefluxthroughtheloopis0,andcurrentflowsinthecounterclockwisedirection.BThefluxthroughtheloopis0,andcurrentflowsintheclockwisedirection.CThefluxthroughtheloopisπWebers,andcurrentflowsintheclockwisedirection.DThefluxthroughtheloopisπWebers,andcurrentflowsinthecounterclockwisedirection.EThefluxthroughtheloopisπWebers,andthecurrentis0.正确答案：E第9题单选题(1分)Twoidenticalinductorsofinducta