《E导体与电介质》PPT课件

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1、§1ConductorsintheElectrostaticField§2DielectricsandPolarizationintheElectricField§3CapacitanceandCapacitor§4TheEnergyofElectricfieldChapter6ConductorsandDielectricsintheElectrostaticField§5Application1ElectrostaticEquilibriumInelectricconditionsallthefreeelectronareatrest2C

2、onditionsofElectrostaticEquilibriumTheelectricfieldiszeroinsideaconductorProving1Notangentialcomponentcanexistab－－－++Proving2§1ConductorsintheElectrostaticFieldCorollary1Theconducingsurfaceisanequipotentialsurface,andallpointsintheinteriorareatthesamepotentialasthesurfaceCo

3、rollary2Thefieldatthesurfaceoftheconductor(andjustoutside)isperpendiculartothesurface3DistributionofChargea)AllofthechargesisonthesurfaceoftheconductorProve：b)TheelectricfieldonthesurfaceofaconductorsNote:Thefieldatthesurfaceoftheconductor(andjustoutside)c)DistributionofCha

4、rgeofSphericalConductorRestrictingfactors：theelectricfieldiszeroinsideaconductor.E=0qConductorshell（腔）(1)NochargeinaconductorshellaTheelectricfieldiszeroinsideinsideconductorandshell导体内、空腔内场强皆为零；bTheconductorandshellareequipotential导体、空腔为等势体；cThechargemustlieonthesurface内表面

5、处处没有电荷，电荷只分布在外表面.(2)AchargeqinaconductorshellOntheinnersurfaceoftheshellthechargeis-q.Ontheoutersurfaceoftheshellthechargeisq.ItisdeterminedbyGauss’slaw.5ElectrostaticScreening静电屏蔽ElectrostaticScreening:InsulatingtheinfluenceofelectricfieldusingconductorshellNomatterthechan

6、geofchargeAtheforceonBchargealwaysiszero.A电荷变化,B电荷受力总是为零。Thechargeinsideshellcanbeshielded壳可以屏蔽内部IfthechargeBischanged,theforceonthechargeAischangedtoo.B电荷变化，A电荷受力会变化。ThechargeAoutsideshellcannotbeshielded壳不能屏蔽外边电荷A。A。BIftheshellistheground,theinfluencebetweenAandBisnotexis

7、t.接地导体壳，可以使壳内外的电荷彼此不影响。例：球形壳C，电荷A带＋q,B带＋Q，r远大于R。求:A，B，C彼此之作用力。解：(1)A、B之间作用力：(2)A、C对B来说是带电量q的点电荷，B受力：(3)静电屏蔽，A受力F=0+QBA+qCrR(4)A、C之间作用力：(5)B、C之间作用力F＝0(6)C接地，A、B受力为零问题：导体壳是否真的能够屏蔽掉外电场使其不能进入腔内？答：接地导体壳return电介质中不存在自由电荷，在电场中会发生极化现象。极性介质：HCl、SO2、H2O非极性介质：O2H2CO21Dielectricpolariz

8、ation无外电场时，电偶极矩取向杂乱或为零，整个介质呈电中性。当有外电场时，非极性分子产生极化，极性分子趋向外场排列，介质表面产生束缚电荷。E---2Polari