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Unformatted text preview: Husain, Zeena Homework 10 Due: Apr 5 2004, 4:00 am Inst: Sonia Paban 1 This printout should have 26 questions. Multiplechoice questions may continue on the next column or page find all choices before making your selection. The due time is Central time. 001 (part 1 of 3) 10 points Given: = 1 . 25664 10 6 Tm / A . An infinite sheet of current, perpendicular to the x axis, located at x = 0 . The linear current density + z flows in the + z direction. By inspection we expect the magnetic field direction b B x , on the positive x side of the sheet (on the righthand side of the sheet) to be in the + y direction, while the magnetic field on the negative x side of the sheet (on the lefthand side of the sheet) to be in the y direction; x y z infinite current sheet in y,z plane Current in + z direction, as shown by arrows. B B We choose the Amperian loop as the dashed line below with sides of length and w . B B w x y The magneto motive force, defined by M = I ~ B d~s, is given by 1. M = 2( + w ) B . 2. none of these. 3. M = 2 B . correct 4. M = ( + w ) B . 5. M = B . 6. M = 2 w B . 7. M = w B . Explanation: Basic concepts Amperes law I ~ B d~s = I . Solution The magneto motive force is given by M = I ~ B d~s, where the integral is around the Amperian loop. Only the sides of the loop contribute, since ~ B d~s = 0 on the top and bottom. On the sides of the loop, ~ B and d~s are parallel, so ~ B d~s = B ds . L = Z B ds Z B ds = B + B = 2 B . 002 (part 2 of 3) 10 points The current encircled by the Amperian loop is 1. I enc = + z . correct 2. I enc = 2( + w ) + z . 3. I enc = w + z . 4. I enc = ( + w ) + z . 5. I enc = 2 + z . Husain, Zeena Homework 10 Due: Apr 5 2004, 4:00 am Inst: Sonia Paban 2 6. I enc = 2 w + z . Explanation: The current enclosed by the loop is given by the current per unit length times the length I enc = + z . 003 (part 3 of 3) 10 points Given : = 0 . 3 m , w = 0 . 065 m , and + z = 3 . 15 A / m . Find the magnitude of the magnetic field k ~ B k . Correct answer: 1 . 9792 10 6 T. Explanation: From Amperes law L = I ~ B d~s = I enc 2 B = + z . Therefore B = 2 + z = 4 10 7 2 (3 . 15 A / m) = 1 . 9792 10 6 T . Note: Fourth of six versions. 004 (part 1 of 1) 10 points A metal bar spins at a constant rate in the magnetic field of the Earth as in Figure. The rotation occurs in a region where the compo nent of the Earths magnetic field perpendic ular to the plane of rotation is 2 . 9 10 5 T. The bar is 0 . 54 m in length and its angular speed is 5 ....
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This note was uploaded on 10/13/2009 for the course PHY 303K taught by Professor Turner during the Spring '08 term at University of Texas at Austin.
 Spring '08
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