Lecture 11 feb7PREVIEW - Lecture 11 EMF, Energy, and Power...

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Unformatted text preview: Lecture 11 EMF, Energy, and Power in DC circuits Reminder Contact your discussion instructor if you have a special problem with Mastering Physics---At his discretion he may choose to extend a deadline, correct a grading problem etc. This is their callnot mine. Microscopic view of metal conduction Free Electrons in a metal are highly scattering---their net displacement is very small compared to the distance traveled. They DRIFT slowly to right against E. The drift speed is so low that it might take a day to get across our lecture hall! Lets see why.-- - - - - - A - - - - - - - - -- - - - - - v d dt e drift Shaded volume has dQ dQ = q N e dQ = qndV = qnAv d dt Where n is free electron density I = dQ/dt = qnv d A J = I/A = qnv d n is huge! ~10 29 electrons/m 3 Hence nq ~ 10 10 C/m 3 The concept of electron drift velocity in section 25.1 is important. The theory of metallic conduction in 25.6 should be read to give more physical meaning to this, but Im not as concerned about the details in 25.6 Electron drift velocity (Average velocity of all conduction electrons) V(=V...
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This note was uploaded on 04/04/2008 for the course PHYSICS 240 taught by Professor Davewinn during the Spring '08 term at University of Michigan.

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Lecture 11 feb7PREVIEW - Lecture 11 EMF, Energy, and Power...

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