電磁場基本理論

數(shù)值法：全貌框圖電磁場基本理論

Section1:Maxwell'sEquations

Maxwell基本方程組、力學(xué)關(guān)系、本構(gòu)關(guān)系、邊界條件、電荷與能量守恒定理、Poynting‘s定理、介質(zhì)電磁模型、導(dǎo)體電磁模型、等離子電磁模型*問題考慮？？？主要學(xué)問點(diǎn)：1.1Maxwell’sEquationsThequantitiesDandBaretheelectricandmagneticfluxdensitiesandareinunitsof[coulomb/m2]and[weber/m2],or[tesla].Bisalsocalledthemagneticinduction.Thequantitiesρa(bǔ)ndJarethevolumechargedensityandelectriccurrentdensity(chargeflux)ofanyexternalchargesThechargeandcurrentdensitiesρ,Jmaybethoughtofasthesourcesoftheelectromagneticfields.Thegeneratedelectricandmagneticfieldsareradiatedawayfromthesesourcesandcanpropagatetolargedistancestothereceivingantennas.Awayfromthesources,thatis,insource-freeregionsofpace,Maxwell’sequationstakethesimplerform:1.1Maxwell’sEquations1.2LorentzForceTheforceonachargeqmovingwithvelocityvinthepresenceofanelectricandmagneticfieldE,BiscalledtheLorentzforceandisgivenby:Volumechargeandcurrentdistributionsρ,Jarealsosubjectedtoforcesinthepresenceoffields.IfJarisesfromthemotionofchargeswithinthedistributionρ,thenJ=ρvThequantityv·f=ρv·E=J·Erepresentsthepowerperunitvolumeoftheforcesactingonthemovingcharges,thatis,thepowerexpendedby(orlostfrom)thefieldsandconvertedintokineticenergyofthecharges,orheat.Ithasunitsof[watts/m3].Wewilldenoteitby1.2LorentzForceWewillfindthatelectromagneticenergyflowingintoaregionwillpartiallyincreasethestoredenergyinthatregionandpartiallydissipateintoheat1.3ConstitutiveRelations1.3ConstitutiveRelationsIninhomogeneousmaterials,thepermittivitydependsonthelocationwithinthematerial:Inanisotropicmaterials,dependsonthex,y,zdirectionandtheconstitutiverelationsmaybewrittencomponent-wiseinmatrix(ortensor)form:Innonlinearmaterials,maydependonthemagnitudeEoftheappliedelectricfieldintheform:1.3ConstitutiveRelationsMaterialswithfrequency-dependentdielectricconstant(ω)arereferredtoasdispersive.1.3ConstitutiveRelations1.4BoundaryConditionsTheboundaryconditionsfortheelectromagneticfieldsacrossmaterialboundariesaregivenbelow:1.5ConservationLaws1.5ConservationLaws1.8HarmonicTimeDependenceThroughtheinverseFouriertransform,generalsolutionsofMaxwell’sequationcanbebuiltaslinearcombinationsofsingle-frequencysolutions:Someinterestingtimeaveragesinelectromagneticwaveproblemsarethetimeaveragesoftheenergydensity,thePoyntingvector(energyflux),andtheohmicpowerlossesperunitvolume.1.9.1SimpleModelsofDielectrics：電子基本電量；E：電場強(qiáng)度m:電子質(zhì)量：自諧振頻率；：電場頻率1.9SimpleModelsofDielectrics

ConductorsSinceinametaltheconductionchargesareunbound,wemaytake1.9.2SimpleModelsConductorsThesteady-statecurrentdensityresultsintheconventionalOhm’slaw:PowerLossesTodescribeamaterialwithbothdielectricandconductivityproperties,theconceptofeffectivedielectricconstantisused.1.9.2SimpleModelsConductorsAconvenientwaytoquantifythelossesisbymeansofthelosstangentdefinedintermsoftherealandimaginarypartsoft