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1、Engineering ElectromagneticsW.H. Hayt Jr. and J. A. Buck,Chapter 5:Conductors and Dielectrics,Current and Current Density,Current Density as a Vector Field,Relation of Current to Charge Velocity,Relation of Current Density to Charge Velocity,Continuity of Current,Energy Band Structure in Three Mater
2、ial Types,Conductors exhibit no energy gap between valence and conduction bands so electrons move freelyInsulators show large energy gaps, requiring large amounts of energy to lift electrons into the conduction band When this occurs, the dielectric breaks down.Semiconductors have a relatively small
3、energy gap, so modest amounts of energy (applied through heat, light, or an electric field) may lift electrons from valence to conduction bands.,Electron Flow in Conductors,Resistance,General Expression for Resistance,Electrostatic Properties of Conductors,Tangential Electric Field Boundary Conditio
4、n,Boundary Condition for the Normal Component of D,Summary,Method of Images,Forms of Image Charges,Example of the Image Method,Example (continued),Example (concluded),Electric Dipole and Dipole Moment,Model of a Dielectric,Polarization Field,dipole moment/vol or C/m2,The number of dipoles isexpresse
5、d as a density, ndipoles per unit volume.,The Polarization Field of the medium is defined as:,Polarization Field (with Electric Field Applied),Migration of Bound Charge,Bound Charge Motion as a Polarization Flux,Polarization Flux Through a Closed Surface,Bound and Free Charge,Gauss Law for Free Char
6、ge,Charge Densities,Taking the previous results and using the divergence theorem, we find the point form expressions:,Electric Susceptibility and the Dielectric Constant,Isotropic vs. Anisotropic Media,Boundary Condition for Tangential Electric Field,Boundary Condition for Normal Electric Flux Density,Example of the Use of Dielectric Boundary Conditions,
