电子信息与通信工程专业英语lesson41太原理工大学版

2021/11/2《电子信息与通信工程专业英语》1Chapter4ElectromagneticFieldandWaveOutline4.1ElectromagneticFieldsTheory4.2Antenna2021/11/2《电子信息与通信工程专业英语》24.1ElectromagneticFieldsTheoryOutlineMaxwell’sequationsCurrentcontinuityequationConstitutiverelationsBoundaryconditionsPowerandenergy2021/11/2《电子信息与通信工程专业英语》3Terminologyvectorn.[数]向量,矢量,带菌者vt.无线电导引scalarn.数量,标量adj.分等级的,数量的,标量的positionvectorn.位矢,方位向量,位置矢量fluxn.[物]流量,通量,涨潮,变迁vi.熔化,流出vt.使熔融,用焊剂处理contourn.轮廓,周线,等高线emfabbr.电动势(electromotiveforce)Stockes’theoremn.斯托克斯定理divergencetheoremn.散度定理conductioncurrentn.传导电流displacementcurrentn.位移电流2021/11/2《电子信息与通信工程专业英语》4solenoidalfieldsn.螺线管磁场,管形场continuityequationn.连续性方程constitutiverelationn.本构关系isotropicadj.等方向性的,各向同性的dielectricconstantn.介电常数relativepermeabilityn.相对磁导率conductivityn.传导性,传导率anisotropicadj.各向异性的tensorn.张量,张肌2021/11/2《电子信息与通信工程专业英语》5In1864,JamesClerkMaxwellproposedoneofthemostsuccessfultheoriesinthehistoryofscience.InafamousmemoirtotheRoyalSociety,hepresentednineequationssummarizingallknownlawsonelectricityandmagnetism.Bypostulatingtheneedforanadditionaltermtomakethesetofequationsself-consistent,Maxwellwasabletoputforthwhatisstillconsideredacompletetheoryofmacroscopicelectromagnetism.Toformacompletefieldtheoryweneedasourcefield,amediatingfield,andasetoffielddifferentialequations.Thisallowsustomathematicallydescribetherelationshipbetweeneffect(themediatingfield)andcause(thesourcefield).IntroductionTexttour2021/11/2《电子信息与通信工程专业英语》6InMaxwell’sequations,thesourcefieldconsistsofthevectorfield(thecurrentdensity)andthescalarfield(thechargedensity),themediatingfieldistheelectromagneticfieldconsistingofthesetoffourvectorfields,,and.),(trJ),(tr),(trE),(trD),(trB),(trH2021/11/2《电子信息与通信工程专业英语》7=electricfieldintensity(vector),volts/meter(V/m)=magneticfieldintensity(vector),ampere/meter(A/m)=electricfluxdensity(vector),coulombs/meter2(C/m2)=magneticfluxdensity(vector),webers/meter2(Wb/m2)=electriccurrentdensity(vector),amperes/meter2(A/m2)=electricchargedensity(scalar),coulombs/meter3(C/m3)EHDBJ2021/11/2《电子信息与通信工程专业英语》8Alltheabovequantities,intime-varyingfields,arearbitraryrealfunctionsofspace,i.e.thepositionvectorr(meters)andtimet(seconds)whiletheyarefunctionsofjustrinthestaticfields.Twonewconceptsshouldbebuilt:theelectricfieldcanbeproducedbychangingmagneticfieldandthemagneticfieldproducedbychangingelectricfield.Sowecallit-----electromagneticfield.2021/11/2《电子信息与通信工程专业英语》9Maxwell’sequationsItsleftsideistheclosed-looporlineintegral(theintegralalongtheclosed-pathline)ofamagneticfieldstrength.Itsrightsideisthesurfaceintegralofthetotalcurrentdensity.Thislawstatesthattheemfεinducedintheclosedpathbyachangingmagneticfieldisequaltothetimerateofdecreaseofthemagneticfluxlinkingtheloop.SdtDJldHCSHSdtBldECS2021/11/2《电子信息与通信工程专业英语》10Thelawsaysthatthemagneticfluxthroughanyclosedsurfaceisequaltozero.ThelawtellsusthattheoutwardfluxofdensityDthroughaclosedsurfaceisequaltothechargeenclosedwithinthesurface.SSdB0SVdVSdDThedifferentialformsofMaxwell’sequationsarelistedbelow:tDJHtBE0BD2021/11/2《电子信息与通信工程专业英语》11Thesefourequationsexplainthetotalrelationshipsbetweenelectromagneticsourcesandthefields:Theconductioncurrentandthedisplacementcurrentarethecurlsourcesofthemagneticfields.Timevaryingmagneticfieldproducinganelectricfield.Themagneticfieldsaresolenoidalfields.Theelectricchargesarethedivergencesourcesoftheelectricfields.2021/11/2《电子信息与通信工程专业英语》12Althoughitisn’tgiveninMaxwell’sequations,wecangetitfromMaxwell’sequations.TheequationofcontinuitycanbeconcludedCurrentcontinuityequationtJ2021/11/2《电子信息与通信工程专业英语》13ConstitutiverelationsToallowauniquedeterminationofthefieldvectors,Maxwell’sequationsmustbesupplementedbyrelationsdescribingthebehaviorofthemediumundertheinfluenceofthefield.Thesesubsidiaryrelationsarecalledconstitutiverelationsthatareestablishedbyexperimentationordeducedfromatomictheory.Ifthefieldvectorsarelinearlyrelatedsothattheprincipleofsuperpositionapplies,themediumissaidtobelinear.AcombinationofMaxwell’sequationsandlinearconstitutiverelationsformsthebasisoflinearelectrodynamics2021/11/2《电子信息与通信工程专业英语》14Amediumissaidtobeisotropiciftheelectricalandmagneticpropertiesatagivenpointareindependentofthedirectionofthefieldatthepoint.If、andhavethesamevaluesateverypointinspace,themediumissaidtobehomogeneous.Ontheotherhand,iftheelectricalandmagneticpropertiesofamediumdependuponthedirectionsoffieldvectors,themediumiscalledanisotropic.2021/11/2《电子信息与通信工程专业英语》15BoundaryconditionsInordertocontinuethesolutionofMaxwell’equationsfromoneregiontoanothersothattheresultingsolutionisuniqueandvalideverywhere,weneedboundaryconditionstoimposeonthefieldvectorsandtheinterface.TheboundaryconditionsbetweenthesetwosetsoffieldsattheinterfacecanbederivedfromtheintegralformofMaxwell’equations.S0h222,,111,,21npillboxInterfaceSasdbc210hltLoopC2021/11/2《电子信息与通信工程专业英语》16Denotetheunitvectorofasthenormaldirectionfrommedium1to