sol-e2-sum10 - Exam II Solutions Phy 2049 Summer 2010 1 At...

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R Problem 3 i Exam II Solutions Phy 2049 Summer 2010 1. At a certain position outside Gainesville, the magnetic field of the Earth is 39 μ T, horizontal to the surface, and directed due North. If the magnitude of the total field is exactly zero 8 cm above a long straight, horizontal wire that carries a constant current i , what is the magnitude and direction of the current? (1) 16 A, west to east (2) 8 A, north to south (3) 16 A, east to west (4) 4.2 A, west to east (5) 8 A, south to north The question was rephrased to, At a certain position outside Gainesville, the magnetic field of the earth is horizontal to the surface, pointed due north, and is 39 μ T in magnitude. If the magnetic field 8 cm above a current carrying horizontal wire is zero, what are the magnitude and the direction of the current? The current carrying wire has to produce a field of 39 μ T, pointed due south, at a distance of 8 cm above it. The current has to be directed west to east. g G ± ² ³ ´µ¶ G· ¸ G ´µ¶ ± ² g = 15.6 A 2. A wire of length L carries a current i . If the wire is bent into a circular coil of N turns and placed into a uniform magnetic field B , what is the magnitude of the maximum possible torque on the loop? (1) L 2 iB/ 4 π N (2) LiB π / 2 N (3)2 L 2 iB/ π 2 N 2 (4) 3 LiB/ π N (5) L 2 π iB/ 4 N 2 The maximum torque on a set of N coils is NIAB. The area A= π r 2 . But the total length of wire used 2 π rN = L. It follows that r = L/2 π N. The answer follows on substitution. 3. A conducting wire is formed into two long, semi- infinite straight sections connected by a quarter circle of radius R , as shown in the figure. What is the magnitude and direction of the magnetic field at the center of the quarter circle? (1) (
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This note was uploaded on 12/05/2011 for the course PHY 2049 taught by Professor Any during the Spring '08 term at University of Florida.

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sol-e2-sum10 - Exam II Solutions Phy 2049 Summer 2010 1 At...

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