Practice HW 14 solution

# Practice HW 14 solution - song (shs546) – Practice HW 14...

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Unformatted text preview: song (shs546) – Practice HW 14 Solutions – weathers – (22202) 1 This print-out should have 9 questions. Multiple-choice questions may continue on the next column or page – find all choices before answering. 001 (part 1 of 4) 0.0 points The figure below shows a straight cylindrical coaxial cable of radii a , b , and c in which equal, uniformly distributed, but antiparallel currents i exist in the two conductors. O i out ⊙ i in ⊗ F E D C r 1 r 2 r 3 r 4 c b a Which expression gives the magnitude of the magnetic field in the region r 1 < c (at F )? 1. B ( r 1 ) = μ i π r 1 2. B ( r 1 ) = μ ir 1 2 π c 2 correct 3. B ( r 1 ) = μ i ( r 2 1 − b 2 ) 2 π r 1 ( a 2 − b 2 ) 4. B ( r 1 ) = μ i ( a 2 − b 2 ) 2 π r 1 ( r 2 1 − b 2 ) 5. B ( r 1 ) = μ ir 1 2 π b 2 6. B ( r 1 ) = μ i ( a 2 − r 2 1 ) 2 π r 1 ( a 2 − b 2 ) 7. B ( r 1 ) = 0 8. B ( r 1 ) = μ i 2 π r 1 9. B ( r 1 ) = μ ir 1 2 π a 2 10. B ( r 1 ) = μ i ( a 2 + r 2 1 − 2 b 2 ) 2 π r 1 ( a 2 − b 2 ) Explanation: Ampere’s Law states that the line inte- gral contintegraldisplay vector B · d vector ℓ around any closed path equals μ I , where I is the total steady current pass- ing through any surface bounded by the closed path. Considering the symmetry of this problem, we choose a circular path, so Ampere’s Law simplifies to B (2 π r 1 ) = μ I en , where r 1 is the radius of the circle and I en is the current enclosed. For r 1 < c , B = μ I en 2 π r 1 = μ parenleftbigg i π r 2 1 π c 2 parenrightbigg 2 π r 1 = μ i parenleftbigg r 2 1 c 2 parenrightbigg 2 π r 1 = μ ir 1 2 π c 2 . 002 (part 2 of 4) 0.0 points Which expression gives the magnitude of the magnetic field in the region c < r 2 < b (at E )? 1. B ( r 2 ) = μ i ( a 2 − b 2 ) 2 π r 2 ( r 2 2 − b 2 ) 2. B ( r 2 ) = μ i ( a 2 − r 2 2 ) 2 π r 2 ( a 2 − b 2 ) 3. B ( r 2 ) = μ ir 2 2 π a 2 4. B ( r 2 ) = μ i ( r 2 2 − b 2 ) 2 π r 2 ( a 2 − b 2 ) 5. B ( r 2 ) = μ i ( a 2 + r 2 2 − 2 b 2 ) 2 π r 2 ( a 2 − b 2 ) 6. B ( r 2 ) = μ i π r 2 7. B ( r 2 ) = μ ir 2 2 π c 2 song (shs546) – Practice HW 14 Solutions – weathers – (22202) 2 8. B ( r 2 ) = μ i 2 π r 2 correct 9. B ( r 2 ) = μ ir 2 2 π b 2 10. B ( r 2 ) = 0 Explanation: For c < r 2 < b , B = μ I en 2 π r 2 = μ ( i ) 2 π r 2 = μ i 2 π r 2 ....
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## This note was uploaded on 04/22/2011 for the course PHYS 2220 taught by Professor Littler during the Spring '00 term at North Texas.

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Practice HW 14 solution - song (shs546) – Practice HW 14...

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