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Unformatted text preview: Kapoor (mk9499) oldhomework 20 Turner (60230) 1 This printout should have 9 questions. Multiplechoice questions may continue on the next column or page find all choices before answering. 001 (part 1 of 2) 10.0 points A circular coil of 255 turns and area 0 . 11 m 2 is in a uniform magnetic field of 0 . 58 T. The maximum torque exerted on the coil by the field is 0 . 0012 N m. Calculate the current in the coil. Correct answer: 7 . 37599 10 5 A. Explanation: Let : = 0 . 0012 N m , N = 255 , A = 0 . 11 m 2 , and B = 0 . 58 T . The maximum torque is = N I A B , so the current in the coil is I = N A B = (0 . 0012 N m) (255) (0 . 11 m 2 ) (0 . 58 T) = 7 . 37599 10 5 A . 002 (part 2 of 2) 10.0 points Assume the 255 turns of wire are used to form a singleturn coil with the same shape but much larger area. What is the current if the maximum torque exerted on the coil by the field is 0 . 0012 N m? Correct answer: 2 . 89255 10 7 A. Explanation: Let : N = 255 . The radius of the coil is r = radicalbigg A . and the total length of the coil is C = N 2 r . The new radius of the singleturn coil is R = C 2 = N r , so the new area of the coil is A new = R 2 = N 2 A . Using the equation for the current, we find the new value of the current: I new = N 2 A B = I N = 7 . 37599 10 5 A 255 = 2 . 89255 10 7 A . 003 10.0 points A circular loop of radius 3 . 12 cm contains 54 turns of tightly wound wire. If the current in the windings is 0 . 668 A and a constant magnetic field of 0 . 408 T makes an angle of 28 . 2 with a vector perpendicular with the loop, what torque acts on the loop? Correct answer: 0 . 0212686 N m. Explanation: Let : r = 3 . 12 cm , N = 54 , I = 0 . 668 A , B = 0 . 408 T , and = 28 . 2 . The torque acting on the loop is: vector = NI vector A vector B Then  vector  = N I  vector A  vector B  sin = N I r 2 B sin = (54)(0 . 668 A) (0 . 0312 m) 2 (0 . 408 T)(sin28 . 2 ) = . 0212686 N m Kapoor (mk9499) oldhomework 20 Turner (60230)...
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 Fall '08
 Turner
 Physics, Work

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