大学物理实验系列——单双电桥讲义.ppt

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1、Chapter25&26MagneticFieldMagneticFluxandGauss’LawTheMagneticForceonaParticleMagneticForceonaCurrent-CarryingWireMagneticFieldDuetoCurrentAmpere’sLawMagneticMaterialsMagnetsusedin:compass(指南针);refrigerator-door;microphone;computerdisk;…Magneticphenomena:25-1.TheDefinitionof(P580)ITh

2、einteractingforcebetweenmovingchargesismagneticforcewhichistransferredbymagneticfield(运动电荷之间的相互作用力---磁力,由磁场传递).Aelectricchargesetupanelectricfieldthatcanaffectotherelectriccharges.Mightyouexpectthatamagneticchargesetupamagneticfieldthatcanthenaffectothermagneticcharges?Suchmagnetic

3、chargesarecalledmagneticmonopoles,whicharepredictedbycertaintheory,althoughtheirexistencehasnotbeenconfirmed.movingchargesmovingchargesmagneticfieldThemagneticforceis:——Lorentz’sforceThemagnitudeof:Thedirectionofisalongthezero-force.(P586)+qInasimilarwayasthedefinitionofelectricfi

4、eld,wecoulddefinebytheactingforceofmagneticfiledonthemovingchargesas:Dimension:I-1MT–2.地磁场Bearth≈510-5TTheprincipleofsuperpositionof:SIunit:tesla(特斯拉)(T),gaussorN/(A·m).AnequivalentwaytodefineintermsoftheforceonelectriccurrentsisdiscussedinSec.25-3(P583).25-2.MagneticFieldLinesand

5、Flux(P581)Noorigin,noterminationandnocrosspoint(无头无尾不相交,闭合曲线);Wraparoundwithcurrent与电流套连;Right-handrulewithcurrent(与电流成右手螺旋关系)1.Thefeaturesofmagneticfieldlines2.Magneticflux&Gauss’lawLet—–numberofmagneticfieldlinethreadingareadA,(Gauss’lawofmagneticfield)Intheabsenceofmagneticmo

6、nopolesthemagneticfluxthreadingaclosedsurfaceiszero.Thefluxofmagneticfieldintersectsaclosedsurface:25-3.MagneticForceonMovingCharges1.Lorentz’sforce(P586)F=qvsin(when=0,F=0),qThechargedparticlesmovinginmagneticfieldactedbymagneticforce:Theforceactingonachargedparticlemovingwithv

7、elocitythroughamagneticfieldisalwaysperpendiculartoand.MagneticforceonlychangemovingdirectionWB=0.2.Themotionofchargedparticleinuniform:+qq-q+Rq>0:,particlestraightlymoveinconstantvelocity.Radiusoftrack:(2)Particlemovesperpendicularto(1)Particlemovesparalleltoq-Rq>0:F=qvB=Candradia

8、llydirected.——Circularmoti