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Unformatted text preview: segovia (cs39966) Homework 5 Spurlock (14441) 1 This printout should have 35 questions. Multiplechoice questions may continue on the next column or page find all choices before answering. 001 10.0 points A circular coil consisting of a single loop of wire has a radius of 19 . 6 cm and carries a current of 37 . 3 A. It is placed in an external magnetic field of 0 . 258 T. Find the magnitude of the torque on the wire when the plane of the coil makes an angle of 25 . 3 with the direction of the field. Correct answer: 1 . 05002 N m. Explanation: Let : r = 19 . 6 cm = 0 . 196 m , B = 0 . 258 T , I = 37 . 3 A , and = 25 . 3 . The area of the circular coil is A = r 2 = (0 . 196 m) 2 = 0 . 120687 m 2 . The torque is bardbl vector bardbl = bardbl vector vector B bardbl = B sin , where is the angle that the normal to the loop makes with the magnetic field, and = I A is the magnetic moment of the loop. Thus the magnitude of the torque is = I A B sin = (37 . 3 A) (0 . 120687 m 2 ) (0 . 258 T) sin(90 25 . 3 ) = 1 . 05002 N m . 002 10.0 points Two long straight wires carry currents per pendicular to the xy plane. One wire carries a current of 97 A and passes through the point x = 11 cm on the x axis. The second wire car ries a current of 12000 A and passes through the point y = 7 . 1 cm on the y axis. What is the magnitude of the resulting magnetic field at the origin? Correct answer: 33803 . 3 T. Explanation: Let : x = 11 cm = 0 . 11 m , I 1 = 97 A , y = 7 . 1 cm = 0 . 071 m , I 2 = 12000 A , and = 4 10 7 T m / A . The magnetic field from the first wire will be vector B 1 = I 1 2 x ( ) directed along the y axis at the origin. The magnetic field from the second wire will be vector B 2 = I 2 2 y ( ) directed along the x axis at the origin. Since these contributions are perpendicular to each other, the magnitude of the total magnetic field at the origin will be B = radicalBig B 2 1 + B 2 2 = radicalBigg parenleftbigg I 1 2 x parenrightbigg 2 + parenleftbigg I 2 2 y parenrightbigg 2 = radicalBigg parenleftBig 2 parenrightBig 2 parenleftbigg I 2 1 x 2 + I 2 2 y 2 parenrightbigg = 2 radicalBigg I 2 1 x 2 + I 2 2 y 2 = 4 10 7 T m / A 2 radicalBigg (97 A) 2 (0 . 11 m) 2 + (12000 A) 2 (0 . 071 m) 2 10 6 T 1 T = 33803 . 3 T . segovia (cs39966) Homework 5 Spurlock (14441) 2 003 10.0 points A long, thin conductor carries a current of 10 . 5 A. At what distance from the conductor is the magnitude of the resulting magnetic field . 000114 T? Correct answer: 1 . 84211 cm. Explanation: Let : = 1 . 25664 10 6 N / A 2 , B = 0 . 000114 T , and I = 10 . 5 A ....
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This note was uploaded on 11/10/2011 for the course PHYSICS 303L taught by Professor Hoffman during the Fall '11 term at University of Texas at Austin.
 Fall '11
 HOFFMAN
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