Engineering Electromagnetic Fields and Waves by Carl Johnk (Wiley) Chapter 3

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1、CHAPTER3Maxwell'sEquationsandBoundaryConditionsforMaterialRegionsatRestMaterialsinnatureareinvariablycomposedofatomsorarrangementsofatomsintoionsormolecules,eachmadeupofpositivelyandnegativelychargedparticleshavingvariousconfigurationsinemptyspaceandvaryingstatesofrelativemotion.Anele

2、ctricormagneticfieldimpresseduponamaterialexertsLorentzforcesupontheparticles,whichundergodisplace•mentsorrearrangementstomodifytheimpressedfieldsaccordingly.TheMaxwellequationswhichdescribetheelectricandmagneticfieldbehaviorinamaterialarethusexpectedtorequiremodificationsfromtheirfre

3、e•spaceversionstoaccountforwhateveradditionalfieldsthematerialparticlesproduce.Itisthetaskinthischaptertodiscusstheseextensionsofthefree•spaceMaxwellequations.Thetopicofconductionisdiscussedfromtheviewpointofacollisionmodel.Thechaptercontinueswithaconsiderationoftheaddedeffectsofelect

4、ricpolarizationwithinamaterial,providingaMaxwelldivergencerelationvalidformaterialsaswellasfreespace.Nextistreatedtheaddedeffectofmagneticpolarization,yieldingasuitablyalteredMaxwellcurlexpressionforthemagneticfield.ThefieldvectorsDandHaretherebydefined.Boundaryconditionsprevailingati

5、nterfacesseparatingdifferentlypolarizedregionsaredevelopedfromtheintegralformsoftheMaxwellequations,tocomparethenormalcomponentsofDandthetangentialcom•ponentsofHatadjacentpointsintheregions.ThediscussioncontinueswithrelatedtreatmentsoftheMaxwelldivBandcurlEequationsformaterial1163-1El

6、ectricalConductivityofMetals117regions,theirintegralforms,andcorrespondingboundaryconditions.Thechapterconcludeswithadiscussionofuniformplanewavesinamaterialpossessingtheparametersu,E,andp.,exemplifyingtheuseoftheMaxwellequationsforalinear,homogeneous,andisotropicmaterial.3-1Electrica

7、lConductivityofMetalsTheelectricandmagneticfieldbehaviorofmaterialregions,solid,liquid,orgaseous,maybecharacterizedintermsofthreeeffects:1.Electricchargeconduction2.Electricpolarization3.MagneticpolarizationForlargeclassesofmaterials,theseeffectsareoftenadequatelydescribedthroughuseof

8、three