物理專業(yè)英語洛倫茲力原文和翻譯

物理專業(yè)英語組別：19組專業(yè)：物理學姓名：9.5 THELORENTZFORCEAchargemovinginamagneticfieldexperiencesaforcewhichweshallcallmagnetic.eforceisdeterminedbythechangq,itsvelocityv,andthemagneticinductionBatthepointwheretheeisatthemontofebeingcnseed.ThetassmpinistatthemagnitudeoftheforceFisproportionaltoeachofthethreequantitiesq,v,andB.Inaddition,FcanbeexpectedtodependonthemutualorientationofthevectorsvandB.ThedirectionoftheerFshudbedeemidbythoeofvetrsvandB.o”cnr”cevcrFformthescalarqandthevectorsvandB,letusfindthevectorofvdBandthenmiythenmuytheresultobtainedythesclarq.TherstistheexprssinqBthasbeenestblsedexeietlythttheforceF

(91）acigonaemoviginamgeicildsderiedbytefruak] （9）Wherekisaproportionalityconstantdependingonthechoiceoftheunitsforthequantitiesinhefrua.tteeinmidthtthereasoningwhihdstoexrssn(.1mutynosbeconsiderdasthederainofEq.(9.32)hisreasningdoesnothaecnlseforce.ItsaimistohelpusmemorizeEq(9.32).Thecorrectnessofthisequationcanbeestablishedolyeprmetly.emtoet.)nenrdsainfeaeccn.TheunitofmagneticinductionB-thetesla-isdeterminedsothattheproportionalityconstantkinEq..2)qasunty.eneInSIuis,tiseutonbeoes] (93）Temagiueofthemgntcfreisn (4)WhereistheanlebewenthevecosvandB.tcanbeseenfrmEq.(.4)thtacageovgalngtelnsofamantcflddesnteprnetheainofamantcfce.ThemagneticforceisdirectedatrightanglestotheplanecontainingthevectorsvandB.Ifthechargeqispositive,thendirectionoftheforcecoincideswiththatofthevector[vB].Whereqisneatve,tedircinsofthevecorsFand[vB]areoposte(Fg..).Sincethemacforceisalasdirctdatrhtanlstothevelctyofadetsokneeeeteeyfadebyacingonitwithaconsatmagnticfed.Theforceexertedonachargedparticlethatissimultaneouslyinanelectricandamagneticfedisq] (3)TispeinwsotedfmterstsfepiesbyheuchhiitedkLrnz(1853~1928)andiscaldtheLrnzfoc.AuethttheeqismgwhthevcyvpaalltoastitiniewirealongwhichthecurrentIflows(Fig.9.7).AccordingtoEqs.(9.30)and(9.34),thechargeinthiscaseeprinesamaneicfrewhoemanideis0v0

2Ib

)Wherebisthedistancefromthechargetothewire.Theforceisdirectedtowardthewirewhenchargeispositiveifthedirectionsofthecurrentandmotionofthechargearethesame,andawayfromthewireifthesedirectionsareopposite(seeFig.9.7).Whenthechargeisnegative,thedietinoftheforceisreered,teotercodiinsbeigequa.Letusconsidertwolikepointchargesqandq2movingalongparallelstraightlineswiththe1evcyvthatismuchrthanc(Fg.98)Whenv,theelticfielddoestvtlyierrmheidofaoryhgs(eSc9.Teeoethemgntdeofte1elcrcforce Fe eetdontechrescnbecnieedeulto1Fe,1=Fe,2=Fe=0

qq12r

(3)Equations（9.21）and(9.33)giveusthefollowingexpressionforthemagneticforce

Fmetdntehgs:FFF0m1 m,2 m

qqv2412r4

(8)(hepoiinvecorrispereniuartov).tsfindtherobeneacdelticfstfollowsfmEq.9.7)nd938tatmv2v2e00c2

)[seeehveobtaindEq.(.39)neasponthtv<isratio，sehvs.，ThersFeand

Fm

aredrd.Figure98hasbendrwnrlieadeheree,esfeslneehetedirctosoftheeleticandmaneicfrcswillbetherveseofthseshwninthefigre.IspctonofE.9sosthttemantcfreiswaertntheoumboneafactorequaltothesquareofratioofthespeedofthechargetothatoflight.Theisthatthemncitrcinbeweengsisariice.Mmwddsaparifthespedoflihtweregea.9.5 洛倫茲力移動磁場力的作用量q度v在磁中所在的位置和該時刻所對應的磁感應強度B力F與qvb，F(xiàn)的方向主要是靠v和B的。F由量q和矢量vB作用得到的，v與B的量q，表達為q[vB] (91）移動電荷在磁場中所受力的作用F。式F=kq[vB] 2）k場例。須住91出92的住92。到92式度。磁感度B的單位——特斯拉——已經(jīng)被定義。所以與在9.32式中等比量k是單為F=q[vB] (3)力小F=qvBsin （9）是v和B的矢量夾角。從9.4式會受到力。磁場力的方向在v和BF矢量向與[vB]所指的方向相同，若所帶電量為負電荷，則與[vB]所指方向相反（見圖9.6）粒磁但產(chǎn)。電荷在既有電場又有磁場的空間中運動。受到的力為F=qE+q[vB] （95）這個表達式亨德克15319名倫。帶子q以速度v流I圖9.7據(jù)9.30和94在實驗中受到力的大小為02IF=vqB=qv (3)b是指流I02I力的向直當帶電力在樣。假設倆同荷qq沿著磁感應線方向以相同的速度v運動其中v小于c1 2當v《c見3電1場力的大小為可表示為1Fe,1=Fe,2=Fe=0

qq1