静电学教学教程电子教案.ppt

Click to edit Master title style,Click to edit Master text styles,Second level,Third level,Fourth level,Fifth level,July 2003,EEB641(Fields,T&P)-Electrostatics,*,Fields(T1)T&P(T2),Class Discussion,Why is electromagnetics(EM)important?,Previous class knowledge in electromagnetic fields.,Outline of Fields Lectures,Electrostatics,Magnetostatics,Quasistatic fields,Time varying fields,magnetic(Faradays Law),electric(displacement current)(Maxwells discovery),the relationship between electric and magnetic fields,(Maxwells equations),Feb 2007,1,EEB641(Fields,T&P)-Electrostatics,Fields(T1)T&P(T2),Importance of the Topic,To understand existing applications,To develop basic knowledge for future applications,“Trouble shooting”,Lecture Notes,Power point slides available on OLT,“Electrostatics”Web notes expand on PowerPoint slides.,July 2003,2,EEB641(Fields,T&P)-Electrostatics,(EEB641)Fields,T&PElectrostatics,Introduction,Reasons for studying Electrostatic fields,Understanding electrical stress in materials high local fields for breakdown studies,effect of voids and inclusions on the field and thus life of solid dielectric insulation;,Electrostatic Discharge(ESD),(for explosive environments and“chips”),This is very relevant in the modern search for better materials in insulation,Understanding behaviour of electronic devices,EMC,EMI problems,EMF health effects,July 2003,3,EEB641(Fields,T&P)-Electrostatics,Electrostatics,Reasons for studying Electrostatic fields,Capacitive coupling between cores of multicore cables,tracks of a PCB(especially with modern high speed computers);understanding stray capacitance,body potentials;in instrumentation for equipment principles;external effects from capacitive coupling;,The above important for design of circuit boards,instrumentation and measurement and studying the affects of fields on humans(note research on aerosols),Application in printers,electrostatic filters in power stations,Tomography applications,Feb 2007,4,EEB641(Fields,T&P)-Electrostatics,Electrostatics,Modelling of the Electrostatic Field,Engineers need to build models they can use for design,In these notes numerical methods will be used to give us an approach to deal with practical rather that idealised problems.,Models are built up from one basic concept force of a charge at a distance or forces between charges.,July 2003,5,EEB641(Fields,T&P)-Electrostatics,(EEB641)FieldsT&PElectrostatics,Traditional Approach,Develop Vector Algebra&Vector Calculus Concepts,(see,Sadikus,initial chapters-there are plenty of books that develop the theory from the maths angle),Then definitions of field quantities are defined using these mathematical concepts,This is OK if you already know what you are talking about but difficult when first grappling with the ideas.,We will develop any mathematical concepts as they are needed but will concentrate on the physical concepts.,NOTE:math concepts are fine but the physical understanding should come first.In this course a strong emphasis will be placed on understanding the basic concepts,July 2003,6,EEB641(Fields,T&P)-Electrostatics,Electrostatics,The problem to be studied,Develop Understanding by Application,Aims:,Solve the problem for the total capacitance between two parallel bars,Develop an“understanding”of the concepts required to solve this problem,Thus provide a basis for understanding any electrostatic problem we encounter,Examine the problem and assess what we know capacitance,voltage and charge in a parallel plate capacitor,Look at what we need to know -the calculation of fringing and stray capacitance,Feb 2006,7,EEB641(Fields,T&P)-Electrostatics,(EEB641)Fields,T&PElectrostatics,The solution will be generally applicable i.e.the concepts can be developed further to provide a solution to practical problems.,Using calculus we can only obtain solutions to idealised problems to help understanding of the practical problem.,Note that the approach defined in these notes will not be found in a text book it is thus important to pay attention and make sure you understand each step of the development,See OLT on electrostatics site for more detail,July 2004,8,EEB641(Fields,T&P)-Electrostatics,(EEB641)Fields,T&PElectrostatics,The Problem and the approach to the Solution,Problem:How do we calculate the capacitance between parallel tracks on a PCB taking the fringing effects into account.,Use our circuit theory knowledge to develop field concepts(usually the reverse is true),Concepts include:,forces and charges,(how do we know a charge exists),&consequently the,electric field,voltage(or potential),electric flux,flux density,capacitance,Aim:provide concepts and tools to tackle any problem in electrostatics,July 2005,9,EEB641(Fields,T&P)-Electrostatics,Electrostatics,Outline of Lectures,Aspects of the Problem,Charge distribution known,If the charge distribution is known the electric field and all its parameters can be calculated(e.g.capacitance,voltage),Boundary voltage known,However the problem is that,usually,only the voltage on the boundaries of an object(e.g.plates of a capacitor,a transmission line)is known,Solve this more difficult problem by:,develop the ideas of flux,its application and solution of the parallel plate capacitor problem,Develop a 2 dimensional model of a parallel plate capacitor to derive the fringing capacitance,July 2003,10,EEB641(Fields,T&P)-Electrostatics,Electrostatics,Overview of Electrostatics Notes,BASIC CONCEPTS:,(CHARGE,COULOMBS LAW,ELECTRIC FIELD,WORK,ENERGY&POTENTIAL),Reinforce the basic concepts for the electrostatic field(these will continually reappear as the theory is developed),How do we know charge exists?,How is it measured?,What is the electric field and how is it defined?,Voltage:a characteristic of an electrostatic field,How is it defined and calculated?,(note that requires an understanding of integration along a line an operation that occurs frequently in electromagnetics;make sure you can handle simple problems),July 2003,11,EEB641(Fields,T&P)-Electrostatics,Electrostatics,Overview of Electrostatics Notes,FORCE AND FLUX,Extending the idea of a force vector to lines of force(flux)and flux&equipotential lines,A look at flux between two parallel plates,The ideas of flux density and capacitance,Calculating flux over a surface,GAUSSS“LAW”,Integrating flux over a surface(this is also an important concept that re-appears many times in electromagnetics;again make sure you can handle simple problems),Flux over a closed surface with and without enclosed charge,July 2003,12,EEB641(Fields,T&P)-Electrostatics,Electrostatics,Overview of Electrostatics Notes,FIELDS IN MEDIA,BUILDING A MODEL,An overview of the modelling procedure&how a model is defined,subdivision into cells,Writing the cell and model equations,SOLVING THE MODEL,ANALYSING THE MODEL,FIELD PLOTTING,July 2003,13,EEB641(Fields,T&P)-Electrostatics,