ECE-305-Lecture11

# ECE-305-Lecture11 - Engineering Electro-Magnetics...

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Unformatted text preview: Engineering Electro-Magnetics Engineering Electro-Magnetics ECE-305, Lecture 11 Dennis McCaughey, Ph.D. 4 March, 2010 03/04/2010 Dennis McCaughey, ECE305, Fall 2009 2 Homework Homework Problems 6.4 6.6 6.7 and 6.11 Due March 23 03/04/2010 Dennis McCaughey, ECE305, Fall 2009 3 Charges Charges Bound Charges – Bound in place by atomic and molecular forces and can only shift slightly in response to external fields Free Charges – Those free to move and contribute to a current 03/04/2010 Dennis McCaughey, ECE305, Fall 2009 4 Chapter 6: Dielectric Materials Chapter 6: Dielectric Materials Dielectrics become polarized in an electric field Flux density D is greater than it would be in free space Simplified theory: – Treat an atom of the dielectric as two superimposed positive and negative charge regions (a) – Positive charge moves to the right under the influence of E – Negative charge moves in the opposite direction – Displacement can be represented by an electric dipole moment p=Qd + +- E (a) (b)- + d E Q (c) 03/04/2010 Dennis McCaughey, ECE305, Fall 2009 5 Polarization Polarization Total 1 A region of a polarized dielectric will contain dipole moments is defined as the dipole moment per unit volume If the dipoles are alligned in the same d n v i i v N ∆ = ∆ = ∑ p p p p Total Total irection, may have a significant value However, a random orientation may cause to be essentialy zero Define the polarization as the dipole moment per unit volume p p P 2 1 1 lim / n v i v i coulombs m v ∆ ∆ → = = ∆ ∑ P p 03/04/2010 Dennis McCaughey, ECE305, Fall 2009 6 Polarization and flux density Polarization and flux density the bound charge tied to the atoms...
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## This note was uploaded on 09/13/2011 for the course ECE 305 taught by Professor Staff during the Spring '08 term at George Mason.

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ECE-305-Lecture11 - Engineering Electro-Magnetics...

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