# hw 18 - yang(ey942 ohw18 turner(56705 1 This print-out...

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Unformatted text preview: yang (ey942) ohw18 turner (56705) 1 This print-out should have 15 questions. Multiple-choice questions may continue on the next column or page find all choices before answering. 001 (part 1 of 2) 10.0 points A closed circuit consists of two semicircles of radii 48 cm and 25 cm that are connected by straight segments, as shown in the figure. A current of I = 4 A flows around this circuit in the clockwise direction. The permeability of free space is 4 10 7 T m / A. O 2 5 c m 4 8 c m k is upward from the paper I = 4 A I What is the direction of the magnetic field B at point O . 1. vector B bardbl vector B bardbl = correct 2. vector B bardbl vector B bardbl = 3. vector B bardbl vector B bardbl = + k 4. vector B bardbl vector B bardbl = + 5. vector B bardbl vector B bardbl = k 6. vector B bardbl vector B bardbl = + 7. None of these are true. Explanation: If you curve the fingers on your right hand in the direction of the current, the magnetic field points along your thumb. 002 (part 2 of 2) 10.0 points Find the magnitude of the magnetic field at point at point O . Correct answer: 7 . 64454 T. Explanation: Let : r 1 = 48 cm = 0 . 48 m , r 2 = 25 cm = 0 . 25 m , I = 4 A , and = 4 10 7 T m / A . The magnetic field due to a circular loop at its center is B = I 2 R . Because the loop is only half of a current loop, the magnetic field due to the arc 1 is vector B 1 = I 4 r 1 , and the magnetic field due to the arc 2 is vector B 2 = I 4 r 2 . Thus the total magnetic field is vector B = vector B 1 + vector B 2 = I 4 parenleftbigg 1 r 1 + 1 r 2 parenrightbigg = (4 10 7 T m / A) (4 A) 4 parenleftbigg 1 . 48 m + 1 . 25 m parenrightbigg parenleftbigg 10 6 T 1 T parenrightbigg = ( 7 . 64454 T) bardbl vector B bardbl = 1 . 003 10.0 points The closed loop shown in the figure carries a current of 16 A in the counterclockwise direc- tion. The radius of the outer arc is 60 cm , that of the inner arc is 40 cm . Both arcs ex- tent an angle of 60 . The permeability of free space is 4 10 7 T m / A. yang (ey942) ohw18 turner (56705) 2 4 c m C B 6 c m D A O 60 y z Find the component of the magnetic field at point O along the x axis. Correct answer: 1 . 39626 10 6 T . Explanation: Let : r i = 40 cm = 0 . 4 m , r o = 60 cm = 0 . 6 m , I = 16 A , and = 4 10 7 T m / A . The magnetic field due to a circular loop at its center is B = I 2 R . Because the loop is only one-sixth of a current loop, the magnetic field due to the inner arc is vector B i = I 12 r i , and the magnetic field due to the outter arc is vector B o = I 12 r o ....
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## This note was uploaded on 11/21/2010 for the course PHY 56705 taught by Professor Turner during the Spring '10 term at University of Texas.

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hw 18 - yang(ey942 ohw18 turner(56705 1 This print-out...

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