Lecture_04 - Conductors and Insulators Different materials...

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Different materials respond differently to electric field Conductor : contains mobile charges that can move through material Insulator : contains no mobile charges Conductors and Insulators
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Insulator: Electrons are bound to the atoms or molecules. Electrons can shift slightly (<1 Å), but remain bound to the molecule. Individual atoms or molecules can be polarized by external electric field. There are a lot of molecules – the net effect produced by the induced dipoles can be very large. Polarization of Insulators
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Diagram showing polarization of an insulator: Dipoles: exaggerated in size; stretch: degree of polarization No mobile charges: excess charges stay where they are Polarization of Insulators
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Field E at a location of a molecule is a superposition of the external applied field and the field created by other induced dipoles : applied E E p ! ! ! ! " = ! p = ! E applied + ! E dipoles ( ) Simplifying assumption: dipoles applied E E ! ! >> ! p ! " ! E applied Low Density Approximation
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There are charges which can move freely throughout the material E In contrast to an insulator
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This note was uploaded on 02/05/2012 for the course PHYS 272 taught by Professor K during the Spring '07 term at Purdue University-West Lafayette.

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Lecture_04 - Conductors and Insulators Different materials...

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