电磁场与波ppt第一章

ElectromagneticFieldsandWavesFUYingJieEmail:[e-mail]:83689397Office:Room223,CentralBuilding,SiPaiLouCampusImportanceoftheCourseElectromagneticPhysicsElectromagneticFieldsandWavesElectricCircuits,AnalogandDigitalElectronics,ElectricMotorsMicrowaveTechnique,RadioTechniqueElectromagneticCompatibility,Anti-interferenceElectronicCircuits,SignalTransmissionAPlatformCourseElectromagneticsStudyoftheeffectsofelectricchargesatrestandinmotionundercertainconditionswithengineeringapplicationbackgroundLimitedSpace/BoundaryConditionsBriefoftheCourse★StaticElectricFieldsandSteadyElectricCurrents★StaticMagneticFields★SolutionofStaticElectromagneticFieldProblems★TimeVaryingElectromagneticFields★PlaneElectromagneticWavesTransmissionLinesandWaveGuidesAntennasAimoftheCourseAnalysis,Solutions,ConclusionsofElectromagneticProblemsunderConditionsofEngineeringApplicationsHowtoLearntheCoursePreparationLectureReviewHomework,independentlyReferences★DavidK.Cheng,FieldAndWaveElectromagnetics，（影印版）清华大学出版社，2007孙国安，电磁场与电磁波理论基础（第二版），东南大学出版社，2003KennethR.Demarest,EngineeringElectromagnetics,科学出版社，2003FawwazT.Ulaby,FundamentalsofAppliedElectromagnetics,科学出版社，2002AboutExamChapter1IntroductionContentMethodUnitsandConstants★Self-StudyTipsVectors:E&D,H&BCoordinates:CartesianCylindricalSphericalOperations:gradientdivergencecurlCharge:Qdensity(line,Surface,volume)Current:Idensity(line,Surface)Chapter2FundamentalsofElectromagneticPhysicsExperimentalLawsMaxwell’sEquationsBoundaryConditionsVectorAnalysis2.1ElectricFieldInteractiveforcesbetweenchargesPositive|NegativeCoulomb’sLawa21isfrom1to2(a21:12)900221211221103614rrqqaFFElectricFieldIntensity(V/m)ElectricFieldIntensityofaPointChargeQqFEq0lim20241lim41rQadqFdErdqQaFdrdqrinanyCoordinatesElectricFieldduetoaSystemofDiscreteChargessourcepoint,fieldpoint/distance,directionexpressioninvectorformnkkkknkkkrnkkrrrrQrQaEEk13121)(4141ElectricFieldduetoaContinuousDistributionofCharges224141rvdaErvdaEdrrρv&ρs&ρlVolumeChargedensityρvSurfaceChargedensityρsLineChargedensityρlVvrrdvaE241SsrrdsaE241LlrrdlaE241Example2-1ChargeQisdistributeduniformlyonacircularringofradiusa.Determinetheelectricfieldintensityatapointontheaxisoftheringinfreespace.Solution:CoordinatesGauss’sLawV-Sor-SVSdvQsdE1ElectricFieldLine(Streamline)ElectricFluxDensity(C/m2)VSDdvQsdDEDElectricPotentialChargeqisverysmall(q0)!!0212112212121CexldEldEqAVVldEqldFAExample2-2ChargeQdistributeduniformlyonasphericalsurfaceofradiusa.Determinetheelectricfieldintensityinfreespace.Solution:GaussianSurface+Coordinates2.2MagneticFieldMovingchargeforcedbyMagneticField.magneticfluxdensity(TorWb/m2)BldIFdBvdqFdBiot-Savart’sLawCrrrraldIBdVraJBdraldIBd222444)/(104700mHrar:sourcefieldExample2-3FindthemagneticfluxdensityatapointontheaxisofacircularloopofradiusathatcarriesadirectcurrentI.Solution:Gauss’sLawforMagneticsLawofconservationofmagneticfluxorPrincipleofcontinuityofmagneticflux0SsdBMagneticFieldIntensity(A/m)HBAmpere’sLawSkkCsdJIldBSkkCsdJIldHExample2-4Aninfinite,solidcylinderofradiusathatcarriesI.Determinethemagneticfieldintensitydistribution.Solution:2.3Faraday’sLawElectromagneticInductionLawElectromotiveForce(emf)(bytheright-handrule)CsSemfldEsdBdtddtdVStationaryLoopinaTime-varyingMagneticFieldtransformeremfSSemfsddtBdsdBdtdVMovingLoopinaStaticMagneticFieldmotionalemfCCsemfsldBvldEVBvdqFdE)(MovingLoopinaTime-varyingMagneticFieldldBvsddtBdVCSemf)(2.4Maxwell’sEquationsExperimentalLawsSCSCSVSsddtBdldEsdJldHsdBdvsdD0DisplacementCurrentDensityTotalCurrentAmpere’sLawSCsdtDJldH)(tDJd0)(SStotalsdtDJsdJIntegralformofMaxwell’sEquations0)(SVSSCSCsdBdvsdDsddtBdldEsdtDJldHDifferentialformofMaxwell’sEquationsPointProperty0BDdtBdEtDJHExample2-5Uniformlydistributedchargewithavolumechargedensityofinthesphericalspaceofradiusa.Determinetheelectricfluxdensityandverifydivergenceoftheelectricfluxdensity.Solution:Example2-6Aninfinite,solidcylinderofradiusathatcarriesI.Determinethemagneticfieldintensitydistributionandverifycurlofthemagneticfieldintensity.Solution:ConservationofCharge(Continuity)MediumPropertiestJEJHBEDcTotalCurrentConductionCurrentConvectionCurrentDisplacementCurrenttDJJJcctotal212.5BoundaryConditionsTangentialNormalElectricFieldMagneticField021ttEE021nnBB021snnDD021lttJHHVectorFormTangentialNormalElectricFieldMagneticField0)(21EEn0)(21sDDn0)(21lJHHn0)(21BBnn:122.6PoyntingVectorPostulatedbyJohnH.Poyntingin1884todefinetheelectromagneticpowerHEPDecreaserateofelectromagneticenergy=Powerdissipation+LeavingPowerisaPowerDensityVectorVVSdVHEdtddVEsdHE)2121()(222VdVHEdtd)2121(22VVdVEJdVE2sdHES)(HEPExample2-5Inanperfectcoaxialcable,voltageUisappliedbetweenitsinnerconductor(ofradiusa)andouterconductor(ofinner