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Unformatted text preview: Lecture #4 Electric Flux, Φ E , and Gauss’s Law (Chapter 22) 30 Min E&M survey quiz (1 extra credit point for participation) is open til 10 pm Friday 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 ∞) 3. 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 ┴ 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……....
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This note was uploaded on 02/15/2012 for the course PHYS 240 taught by Professor Winn during the Winter '11 term at University of Michigan.
 Winter '11
 Winn
 Force

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