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1、PROBLEMS_18-1ElectricalPotentialEnergy1.A3mCchargeisbroughtinfrominfinityandfixedattheoriginofacoordinatesystem.(a)Howmuchworkisdone?(b)Asecondcharge,of5mC,isbroughtinforminfinityandplaced10cmawayfromthefirstcharge.Howmuchdoestheelectricfieldofthefirstchargedowhen
2、thesecondchargeisbroughtin?(c)Howmuchworkdoestheexternalagentdotobringthesecondchargeinifthatchargemoveswithunchangingkineticenergy?2.Achargeof4mCisplacedatthepointx=2,y=3,z=0(alldistancesgivenincentimeters).Calculatetheworkdoneinbringachargeof-8mCfromx=2,y=15,z=-
3、30tothepointx=2,y=12,z=6,assumingthatthechargeismovedatasteadyspeed.3.Deriveanexpressionfortheworkrequiredtosetupthefour-chargeconfigurationofFig.18-15,assumingthechargesareinitiallyinfinitelyfarapart.LetV=0atinfinite.aaaa+q+q-q-qFig.18-15Problem3.4.Twopointcharge
4、sarelocatedonthex-axis,atandat.(a)Findtheworkthatmustbedonebyanexternalforcetobringathirdpointchargefrominfinityto.(b)Findthetotalpotentialenergyofthesystemofthreecharges.5..AparticleofpositivechargeQisfixedatpointP.Asecondparticleofmassmandnegativecharge–qmovesat
5、constantspeedinacircleofradiusr1,centeredatP.DeriveanexpressionfortheworkWthatmustbedonebyanexternalagentonthesecondparticletoincreasetheradiusofthecircleofmotiontor2.18-2ElectricPotential6.Charges+q,-q,+q,and-qareplacedonsuccessivecornersofasquareinthexy-plane.Pl
6、otalllocationsinthexy-planewherethepotentialiszero.7.Theoriginofacoordinatesystemisattheintersectionpointoftheperpendicularbisectorsofthesidesofanequilateraltriangleofsides10cm.Calculatethepotentialattheoriginduetothreeidenticalchargesof0.8mCplacedatthecornersofth
7、etriangle.8.AchargeQisdistributeduniformlyoverthesurfaceofasphericalshellofradiusR.Howmuchworkisrequiredtomovethesechargestoashellwithhalftheradius?Thechargesareagaindistributeduniformly.9.CalculatethepotentialinsideandoutsideasphereofradiusRandchargeQ,inwhichthec
8、hargeisdistributeduniformlythroughoutthesphere.10.AsaspaceshuttlemovesthroughthediluteionizedgasofEarth’sionosphere,itspotentialistypicallychangedby-1.0
