Lecture 4 jan15

# Lecture 4 jan15 - Lecture #4 Electric Flux, E, and Gauss's...

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Lecture #4 Electric Flux, Φ E , and Gauss’s Law Qwizdom session ID# is “240” all term

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Electric Field Lines (Faraday’s Lines of Force) (helpful visualizer of ) E Electric Field lines are drawn such that: 1. at any point is tangent to the line 2. Lines begin on + charge (or ∞), end on - (or ∞) 1. E is large where the lines are closely spaced E Reminder from last lecture…. Let’s make #3 more quantitative……. .
Point #3 improved (better) (E = # of lines, N, per area, A , perpendicular to E) = A N E BUT……what if E is varying in magnitude and/or direction over A?? Solution: we need to shrink A down to an infinitesimal, dA

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Point #3 improved (best) = = dA dN E E Shrink A to an infinitesimal dA and consider the infinitesimal number of lines dN poking through it. The ratio is the E field at that point: This is a dumb way to define our most fundamental concept of E!! Turn it around to define N in a fundamental fashion……. = EdA dN How do we get dA at a selected point on some arbitrary surface???
The outward surface normal

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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 4 jan15 - Lecture #4 Electric Flux, E, and Gauss's...

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