20 AmperesLaw(1)

# 20 AmperesLaw(1) - Summary Lecture 19 Total B-field is...

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Craig Ogilvie 11 Summary Lecture 19 § Total B-field is vector sum of B-fields from each current element Superposition Split complex wire arrangements into simple elements § Force on parallel current carrying wire due to the B-field of the other wires pairs of wires exert equal and opposite forces » Newton’s Third Law

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Craig Ogilvie Calculating Fields, E and B 22 0 ε encl q A d E = ∫ ∫ Gauss Law r r q E ˆ 4 1 2 0 πε = Coulomb Law ˆ 4 2 0 r r v q B × = π μ Biot-Savart Law i d intercepte 0 = l d B Ampere’s Law always true, can always use, but requires superposition always true: useful to get E or B , Useful when charge, current distributions are symmetric
Craig Ogilvie 33 Goal Today: Ampere’s Law § Pre-lecture video described line integral around closed loop Current that intercepts, goes through loop. § Understand how to use Ampere’s Law § Understand when you can effectively use Ampere’s Law to calculate B-field § Two ways of calculating B-field (Ampere’s, Biot-Savart) useful in different cases i d intercepte 0 μ = l d B

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Craig Ogilvie 44 Question: Four Amperian Loops, 1st round Three equal currents carrying i, rank the four Amperian loops according to the magnitude of | | l d B 1. a > (d=b) > c 1. a > d > c > b 2. d > (a=b) > c 3. d > (a=c) > b 1 of 300
Craig Ogilvie Question: Four Amperian Loops, 2nd round 0% 0% 0% 100% 0% 0% 0% 100% 1 2 3 4

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## This note was uploaded on 09/20/2011 for the course PHYS 222 taught by Professor Johnson during the Spring '07 term at Iowa State.

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20 AmperesLaw(1) - Summary Lecture 19 Total B-field is...

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