英文PPT电磁学Electric_Change 20页

电磁学(Electromagnetism)Thecombinationofelectricalandmagneticphenomena ElectricChargeandElectricFieldStaticElectricityElectricChargeandItsConservationInsulatorsandConductorsInducedChargeCoulomb’sLaw NewWordsandExpressionsstaticcharge静电荷quantized量子化的elementarycharge基本电荷conductor导体insulator绝缘体induce感应Coulomb库仑pointcharge点电荷permittivityoffreespace真空电容率electricfield静电场testcharge试验电荷 (a)Rubaplasticruler(b)bringitclosetosometinypiecesofpaper.ElectricChargeandItsConservationInsulatorsandconductorsInducedCharge1Staticelectricity 1.Electriccharge(电荷)Itisanintrinsiccharacterofthefundamentalparticlesmakingupthoseobjects.Chargeswiththesamesignrepeleachotherandchargeswithoppositesignsattracteachother.Thatis:unlikechargesattract,likechargesrepelChargeisanintrinsicpropertyofmatter.Twotypes:PositiveCharge:ProtonsNegativeCharge:Electrons Thenetamountofelectricchargeproducedinanyprocessiszero.3.TheSIunitofchargeistheCoulombTheSIunitofchargeisthecoulomb(C).2.Lawofconservationofelectriccharge 4.Electricchargeisquantizedq=n|e|,wherenisapositiveornegativeinteger,andeisaconstantofnaturecalledtheelementarycharge(基本电荷).1|e|=1.60×10-19C.物体带电量都是基本电荷的整数倍。电荷的这种特性叫电荷的量子性(quantized)。Alltheelectrons/protonshaveidenticalelectriccharge.2)Alltheelectricchargesofchargedbodyareintegraltimesofthatofanelectron/proton. Thechargeofanelectronis:Thechargeofaprotonis:UnitCistheabbreviationofCoulomb1Cofchargeisequaltothemagnitudeofthechargeofelectrons. Conductorsarematerialsinwhichsomeofnegativechargecanmovefreely.5.ConductorsandInsulatorsnonconductors（insulators）semiconductorssuperconductors ConductorsandInsulators（导体和绝缘体）Mostthingsareinbetweenperfectconductor/insulator22Electronsarefreetomoveinaperfectconductor.Electronsstaywiththeiratominanperfectinsulator.Semiconductors(半导体) 6.Themethodstogetelectriccharges1)Chargedduetorubbing(摩擦起电)(a)Rubaplasticrulerand(b)bringitclosetosometinypiecesofpaper. 2)InducedCharge(感应起电)Apositivelychargedobjectisbroughtclosetoaneutralmetalrod.Neutralmetalrodmetalrodstillneutral,butwithaseparationofchargeChargesmoveandleaveapositivechargeattheoppositeend.Itissaidtobeinduced(感应). Coulomb"sLaw 1.Pointcharge(点电荷)当带电体的线度与它到其它带电体之间距离或到研究点之间的距离相比足够小时(d<