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1、Physics42Exam3Fall2013PRINTName:___________________________________1234ConceptualQuestions:CircletheBESTanswer.(1pointeach)1.Asmallplasticballhasanexcessnegativechargeonit.Ifamagnetisplacedclosetothisball,itwilleitherattractorrepeltheball,dependinguponwhichpoleisc
2、losertotheball.A)TRUEB)FALSE2.Alongstraightwirehasaconstantcurrentflowingtotheright.Asquareringissituatedabovethewire,andalsohasaconstantcurrentflowingthroughit(asshownbelow).Whichofthefollowingstatementsistrue?A)Thenetmagneticforceontheringisupward,andthereisalso
3、anettorqueonthering.B)Thenetmagneticforceontheringiszero,andthenettorqueiszero.C)Thenetmagneticforceontheringisdownward,andthereisalsoanettorqueonthering.D)Thenetmagneticforceontheringiszero,butthereisanettorqueonthering.E)Thenetmagneticforceontheringisdownward,an
4、dthenettorqueiszero.3.Aftertheswitchhasbeenclosedforalongtime,thecurrentintheLRcircuitiszero.a.TRUEb.FALSE4.Asolenoidconsistsof100circularturnsofcopperwire.Partsofthreeturns,A,BandC,areshownbelow.Whenacurrentflowsthroughthecoil,a.bothAandCarerepelledbyB.b.Aisattra
5、ctedtoB;CisrepelledbyB.c.neitherAnorCisattractedtoorrepelledbyB.d.AisrepelledbyB;CisattractedtoB.e.bothAandCareattractedtoB.5.AsanairplanefilesnorthfromSanFranciscotoSeattle,itpassesthroughtheEarth’smagneticfield.Asaresult,amotionalemfisdevelopedbetweenthewingtips
6、.Whichwingtipispositivelycharged?a)theleftwingb)therightwingc)chickenwingd)neither6.Whenaferromagneticmaterialisplacedinanexternalmagneticfield,themagneticfieldstrengthisA)increasedB)decreasedC)nochange.7.Whenaferromagneticmaterialthathasbeenmagnetizedisbroughttoa
7、temperaturegreaterthantheCurietemperature,whathappenstoitsresidualmagnetism.a.Nothinghappenstotheresidualmagnetism.b.Theresidualmagnetismdisappears.c.Theresidualmagnetismreachesit’shighestvalue.d.Allthemagneticdomainscausingmagnetismbecomeasingledomain.e.Themateri
8、alofthemagnetmeltscausingcurrentsthataremagnetic.8.Acurrent-carryingwireispulledawayfromaconductingloopinthedirectionshown.Asthewireismoving,isthereacwc
