北京理工大学电磁场Ch.1PPT课件.ppt

北京理工大学Beijing Institute of Technology电磁场理论（第一讲）Electromagnetic Field Theory (Lecture 1)Electromagnetic Field Theory (Lecture 1)盛新庆（Sheng Xin-Qing）电磁仿真中心（Center for Electromagnetic Simulation）北京理工大学信息科学技术学院（School of Information Science and Technology，Beijing Institute of Technology）电子信箱： 电话:68949049http:/ 1.北京理工大学Beijing Institute of TechnologyOutlineA Brief Introduction of This Course Explain the title;Importance;Contents;Reference books;The Physical Background of Establishing Electromagnetic Wave Theory2 2.北京理工大学Beijing Institute of TechnologyTitle of This CourseElectromagnetic Field TheoryElectromagnetic Wave TheoryElectric Electrics Electronics Magnetic MagnetismTheory:A statement or group of statements established by reasoned argumentbased on known facts,intended to explain a particular fact or event (Longman Dic.)Set of reasoned ideas intended to explain facts or events (Oxford Dic.)人们由实践概括出来的关于自然界和社会的知识的有系统的结论 （现代汉语词典）3 3.北京理工大学Beijing Institute of Technology Importance of This CourseOne of Fundamental Courses in Our Information Age Wireless Communications(Satellite communication Mobile Phone),Radar,et al.stealthy aircraft,low-observable targetsOne of Masterworks in the whole mankind civilization history4 4.北京理工大学Beijing Institute of Technology Content of This CourseHow is Electromagnetic Field Theory established?(Ch.1)Physical Background,Mathematical Background,Academic Tradition BackgroundHow to employ Electromagnetic Field Theory to solve the typical problems in the current information Age?Propagation and Transmission,Radiation,Scattering (Ch.2,Ch.3,Ch.4)5 5.北京理工大学Beijing Institute of TechnologyReference Books of This Course电磁波述论，盛新庆，科学出版社Field and Wave Electromagnetics，David K.Cheng,清华大学出版社Exercise Problems：http:/6 6.北京理工大学Beijing Institute of TechnologyRequirement of This CourseYou are required to do exercises and examinations in English.7 7.北京理工大学Beijing Institute of TechnologyPhysical Background of Establishing Electromagnetic Wave TheoryKnowledge in Electrics and Magntism Before Coulombs LawAfter Coulombs Law8 8.北京理工大学Beijing Institute of TechnologyBefore Coulombs LawEastern 100BC-100A.D.triboelectricity,triboluminescence 500BC magnetic stone1000A.D.Compass,magnetic declination angle 1600A.D.Electric in Ligntning Western600BC amber1492A.D.magnetic declination angle Observation9 9.北京理工大学Beijing Institute of TechnologyCoulombs LawCoulomb,French,1736-18061784-1785Torsion balance1772 Cavendish 1785 Coulomb 1872 Maxwell 1971 Williams et al.permittivity1010.北京理工大学Beijing Institute of TechnologyAmperes LawOersted,1777-1851,Denmark1820Magnetized needleBiot-Savart-LaplaceAmperes Lawpermeability1111.北京理工大学Beijing Institute of TechnologyFaradays Law1,Varing Electric Current2,Varing Magnetic FieldFaraday,1791-1867,Britain1831Neumann,1798-1895,GermanyElectromotive force1212.北京理工大学Beijing Institute of TechnologyMathematical Background of Establishing Electromagnetic Wave TheoryCalculusNewton,1642-1727,BritianLeibnitz,1646-1716,GermanyVector Analysis Hamilton,1805-1865,BritainGibbs,1839-1903,U.S.AHeaviside,1850-1925,Britain 1313.北京理工大学Beijing Institute of TechnologyVector Analysis Definition of VectorVector RepresentationTransformations of Vector Representation in Different Coordinate Systems1414.北京理工大学Beijing Institute of TechnologyVector Representationxyzzxyz1515.北京理工大学Beijing Institute of TechnologyTransformations of Vector Representation in Different Coordinate Systemsxyzz1616.北京理工大学Beijing Institute of TechnologyVector Addition and Substration？1717.北京理工大学Beijing Institute of TechnologyDot Multiplication of VectorsABCommutative Distributive1818.北京理工大学Beijing Institute of TechnologyCross Multiplication of VectorsABanticommutative 1919.北京理工大学Beijing Institute of TechnologyVector Identities2020.北京理工大学Beijing Institute of TechnologyVector Analysis OperatorsGradientDivergenceCurl 2121.北京理工大学Beijing Institute of TechnologyGradient of a Scalar FieldCartesian CoordinatesCylindrical CoordinatesSpherical CoordinatesThe gradient operator usually operates on a scalar physical quantity,and the result of the operation is a vector whose magnitude equals to the maximum rate of change of the physical quantity per unit distance and whose direction is along the direction of maximum increase.2222.北京理工大学Beijing Institute of TechnologyVector Identities2323.北京理工大学Beijing Institute of TechnologyDivergence of a Vector Field Cartesian CoordinatesCylindrical CoordinatesSpherical CoordinatesDefinitionGauss TheoremNet outward flux of F per unit volume as the volume about the point tends to zero.2424.北京理工大学Beijing Institute of TechnologyExampleIf ,find (or div A)at the point(1,-1,1).At point(1,-1,1)2525.北京理工大学Beijing Institute of TechnologyCurl of a Vector Field Cartesian CoordinatesCylindrical CoordinatesSpherical CoordinatesDefinitionStokess TheoremNet circulation flux of F per unit area as the area about the point tends to zeroDirection is the normal direction of the area 2626.北京理工大学Beijing Institute of TechnologyExampleIf ,find (or curl A)at the point(1,-1,1).At point(1,-1,1)2727.北京理工大学Beijing Institute of TechnologyOften-Used Symbols2828.北京理工大学Beijing Institute of TechnologyVector IdentitiesIf,we can defineVector can expressed as the gradient of a scalar fieldIf ,we can defineVector can expressed as the curl of another vector filed.2929.北京理工大学Beijing Institute of TechnologyVector Identities3030.北京理工大学Beijing Institute of TechnologyVector Theorems First-Kind Scalar Green TheoremSecond-Kind Scalar Green TheoremFirst-Kind Vector Green TheoremSecond-Kind Vector Green Theorem3131.北京理工大学Beijing Institute of TechnologyHelmholtzs Theorem A vector field is determined to within an additive constant if both its divergence and its curl are specified everywhere.3232.北京理工大学Beijing Institute of TechnologyWestern Academic Tradition西方科学的发展是以两个伟大的成就为基础，那就是：希腊哲学家发明的形式逻辑体系（在欧几里得几何学中），以及通过系统的实验发现有可能找出因果关系（在文艺复兴时期）。-爱因斯坦文集第一卷第574页 3333.北京理工大学Beijing Institute of TechnologyDevelopment of Western Academic TraditionEuclid（欧几里得）Euclids Elements 几何原本 I.Newton（牛顿）Mathematical Principle of Natural Philosophy 自然哲学的数学原理I.Kant（康德）Critique of Pure Reason 纯粹理性的批判3434.北京理工大学Beijing Institute of Technology欧几里得 的几何原本 Euclids ElementsEuclidEuclid（300BC）Educated in Plato Academy(柏拉图学院)，lived in Alexander City (亚历山大城)Euclids ElementsEuclids ElementsBegin with definitions and axioms，then prove 467 propositions by reason,include 13 Chs.，3535.北京理工大学Beijing Institute of Technology牛顿的自然哲学的数学原理 Mathematical Principle of Natural PhilosophyMathematical Principle of Natural PhilosophyNewton（1642-1727）Educated in Trinity College of Cambridge Univ.(剑桥的三一学院)，lived in Lincolnshire、Cambridge、London Mathematical Principle of Natural PhilosophyMathematical Principle of Natural Philosophy Three Versions(1687,1713,1726,拉丁文;1729,英文)Mechanics Theory(Three Mechanics Laws and Universal Gravitations Law,reasoned,explain many natural facts,more importantly,accurately predicted natural phenomena)3636.北京理工大学Beijing Institute of Technology康德的纯粹理性的批判 Kants Critique of Pure ReasonKant（1724-1804）受教于哥尼斯堡大学，生活于哥尼斯堡Critique of Pure ReasonCritique of Pure ReasonTwo Versions（1781，1787）Pure investigation on academic tradition founded by NewtonFour Famous Antinomies 3737.北京理工大学Beijing Institute of TechnologyChinese Academic Tradition“博学而笃志，切问而近思，仁在其中矣。”Widely learning and sincerely intend,question precisely and reflect what is at hand,ren will be there -论语论语 (the Analects of Confucius)子张篇第十九What kind of questions are worth to be studied?Questions closely relative to our lifeHow to study?Widely learning and Sincerely Intend3838.北京理工大学Beijing Institute of TechnologyDevelopment of Chinese Academic Tradition孔子（Confucius）论语论语 (the Analects of Confucius)刘徽（Liu-Hui）九章算术注九章算术注Nine Chapters on the Mathematical ArtsNine Chapters on the Mathematical Arts沈括（Shen-Kuo）梦溪笔谈梦溪笔谈3939.北京理工大学Beijing Institute of Technology论语（The Analects of Confucius）Confucius（551BC.9.28-479BC）生于今山东曲阜，曾跟鲁太师习周礼论语论语 (The Analects of Confucius)陈述也采取一问一答式。共有20篇，约11000余字4040.北京理工大学Beijing Institute of Technology刘徽的九章算术注 刘徽（公元260年左右，魏晋时期）Lived in Shandong Province,Zhouping County(生于今山东省邹平县)九章算术注九章算术注（263年）Nine Chapters on the Mathematical ArtsNine Chapters on the Mathematical ArtsContents:Nine mathematical problems concerned peoples life.Style:First list problems and variants,then give the solution procedure.Chapters have no logical relations and no special order.4141.北京理工大学Beijing Institute of Technology沈括的梦溪笔谈沈括（公元1033-1097，北宋）杭州钱塘县人，曾跟鲁太师习周礼梦溪笔谈梦溪笔谈 以笔记的体裁，记录、稽考、订正了大量的当时和前代的典章制度、掌故逸事、文物考古、自然知识等。共609条，其中科技条目约255条，占42%，涉及自然观、乐律、数学、物理、天文、气象、地理建筑、水利等。4242.北京理工大学Beijing Institute of TechnologyComparison of Western and Chinese Academic TraditionChinese Academic Tradition重记录、重“述而不作(narrate,not invent)”（论语述而篇第七），重“学而时习之(practise)”（论语学而篇第一），在反复的咏颂中，以达“其义自见”（艺文类聚卷五十五），“熟能生巧”（归田录卖油翁），“温故而知新”（论语为政篇第二）对材料的整理所下功夫是较少的。这里的“整理”指的是从材料中提炼出观念，并用观念来统领解释材料。4343.北京理工大学Beijing Institute of TechnologyDisadvantages of Western Academic TraditionDisadvantages of Western Academic Tradition更不妨回顾一下思想史罢。许多严密周全的思想和哲学系统经不起时间的推排销蚀，在整体上都垮塌了，但是它们的一些个别见解还为后世所采取而未失去时效。往往整个理论系统剩下来的有价值东西只是一些片段思想。脱离了系统而遗留的片段思想和萌发而未构成系统的片断思想，两者同样是零碎的。眼里只有长篇大论，瞧不起片言只语，甚至陶醉于数量，重视废话一吨，轻视微言一克，那是浅薄庸俗的看法假使不是懒惰粗浮的借口。-钱钟书，七缀集，第33-34页4444.北京理工大学Beijing Institute of TechnologyAdavantages of of Western Academic TraditionAdavantages of of Western Academic TraditionThe tradition makes the materials clear and concise.More importantly,it usually can abstract original ideas from materials,and give people strong faith,bring imagination and cretivity.Strong Power,Imagination,Creativity4545.北京理工大学Beijing Institute of TechnologyComparison of Western and Chinese Comparison of Western and Chinese Academic TraditionAcademic TraditionWestern academic tradition emphasizes abstracting concepts,constructing logical systems,and inventing the future with strong faith.(西学传统以提炼观念，构建逻辑体系，进而以坚定的信念创造未来为基本特征，其长在于条理清晰，创造性极强；其短在于创造的观念往往远离人类生活，容易形而上，华而不实，以偏代全，误入歧途，走向极端。)Chinese academic tradition emphasizes widely learning,practice again and again.(华夏传统以博采、敏感、反复、熟练、温故而知新，以达赏玩游乐之境界为基本精神，其长在于不离人类健康生活的轨道，保证中庸而行；其短也很明显，在于创造性较弱。)4646.北京理工大学Beijing Institute of TechnologyAbstraction from Coulombs LawAbstraction from Coulombs LawElectric Field Intensity and Electric Flux DensityElectric Field Intensity and Electric Flux DensityCoulombs Law4747.北京理工大学Beijing Institute of TechnologyAbstraction from Amperes LawAbstraction from Amperes LawMagnetic Field Intensity and Magnetic Flux DensityMagnetic Field Intensity and Magnetic Flux DensityAmperes Law4848.北京理工大学Beijing Institute of TechnologyAbstraction from Faradays LawAbstraction from Faradays LawFaradays Law4949.北京理工大学Beijing Institute of TechnologyMaxwells ContributionMaxwells ContributionFaradays LawAmperes LawCoulombs LawCoulombs LawAmperes LawMaxwells Displacement Current DensityAmperes LawAmpere-Maxwells Law5050.北京理工大学Beijing Institute of TechnologyExampleExampleConduction currentdarea ADisplacement current5151.北京理工大学Beijing Institute of TechnologyElectromagnetic Field TheoryElectromagnetic Field Theory-Maxwells Equation-Maxwells EquationAmperes LawCoulombs Law5252.北京理工大学Beijing Institute of TechnologyPrediction of Electromagnetic WavePrediction of Electromagnetic WaveAmperes LawCoulombs LawFizeau measured the light speed in 18495353.北京理工大学Beijing Institute of TechnologyElectromagnetic Field TheoryElectromagnetic Field Theory-Maxwells Equation-Maxwells EquationAmperes LawCoulombs LawDifferential FormIntegral Form5454.北京理工大学Beijing Institute of TechnologyPrediction of Electromagnetic WavePrediction of Electromagnetic WaveAmperes LawCoulombs LawFizeau measured the light speed in 18495555.北京理工大学Beijing Institute of TechnologyHertzs ExperimentsHertz did an experiment in 1888 to verify the existence of electromagnetic wave5656.北京理工大学Beijing Institute of TechnologyMaxwells equations predict the existence of electromagnetic waves.They impose no limit on the frequency of the waves.All EM waves in whatever frequency range propagate in a medium with the same velocityMicrowave frequency rangeL band1-2 GHzS band2-4 GHzC band4-8 GHzX band8-12 GHzKu band 12.4-18 GHzK band18-26.35 GHzKa band26.5-40 GHzElectromagnetic spectrum5757.北京理工大学Beijing Institute of TechnologyLight frequency rangeRed0.72mViolet0.38 mWavelength:Frequency:MFMF200-3000kHz200-3000kHzAM,maritimeAM,maritimeHFHF3MHz-30MHz3MHz-30MHzSW radioSW radioVHFVHF30-300MHz30-300MHzTV,FM,policeTV,FM,policeUHFUHF300-3000MHz300-3000MHzRadar,TVRadar,TVSHFSHF3-30GHz3-30GHzRadar,satellite communicationRadar,satellite communicationElectromagnetic spectrum5858.北京理工大学Beijing Institute of TechnologyDetermined Formulation of Electromagnetic ProblemsDetermined Formulation of Electromagnetic Problems Maxwells Equations Constitutive Relations Boundary Conditions5959.北京理工大学Beijing Institute of TechnologyConstitutive Relations 6060.北京理工大学Beijing Institute of TechnologyRelative permittivity of materials(r)VacuumQuartzAirSeawaterWood(dry)Distilled waterDry SoilPetroleum oilGlass6161.北京理工大学Beijing Institute of TechnologyConductivities of materials()silverironcopperseawatergold distilled wateraluminumtransformer oilbrass6262.北京理工大学Beijing Institute of TechnologyBoundary ConditionsFor problem involving contiguous regions of different&,we need to know the boundary conditions:From the integral forms of Maxwells equations,we getFor tangential components,For normal componentsmedium 1medium 26363.北京理工大学Beijing Institute of TechnologyFrom Maxwells equations:(1)Faradays LawFrom Maxwells equations:(1)Faradays LawWhen w tends to 0,E1t=E2tTangential E-field is continuous across an interfaceE1E2E3E4wlmedium 1medium 2yxz6464.北京理工大学Beijing Institute of TechnologyFrom Maxwells equations:(2)Amperes LawFrom Maxwells equations:(2)Amperes LawWhen w tends to 0,Jzw Js,Ht2 Ht1=JsTangential H-field is discontinuous across an interface where a free surface current existsH1H2H3H4wlmedium 1medium 2yxz6565.北京理工大学Beijing Institute of TechnologyFrom Maxwells equations:(3)Gausss LawFrom Maxwells equations:(3)Gausss LawNormal component of D field is discontinuous across an interface where a surface charge exists.The amount of discontinuity being equal to the surface charge densityD1D2medium 1medium 26666.北京理工大学Beijing Institute of TechnologyFrom Maxwells equations:(4)From Maxwells equations:(4)Normal component of B field is continuous across an interfaceB1B2medium 1medium 26767.北京理工大学Beijing Institute of Technology(1)Interface between 2 lossless linear mediaNo free charges and no surface currents at interface between two lossless media(2)Interface between a dielectric and a perfect conductorSpecial Cases6868.北京理工大学Beijing Institute of TechnologyIn solving field problems,good conductors are often considered as perfect conductors in regard to boundary conditions.*The charges can only reside on the surface.Conductivities of materials()silver,copper,gold,aluminum,brass,iron Interior of a perfect conductor,E=0 (otherwise J=E ).Therefore,D=0Interrelationship between(E,D)and(B,H)from Maxwells,B=H=0Interface betwe