oldhw 21 - nguyen (jmn727) oldhomework 21 Turner (59070) 1...

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Unformatted text preview: nguyen (jmn727) oldhomework 21 Turner (59070) 1 This print-out should have 13 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 79 cm and 41 cm that are connected by straight segments, as shown in the figure. A current of I = 5 A flows around this circuit in the clockwise direction. The permeability of free space is 4 10 7 T m / A. O 4 1 c m 7 9 c m k is upward from the paper I = 5 A I What is the direction of the magnetic field B at point O . 1. vector B bardbl vector B bardbl = 2. vector B bardbl vector B bardbl = + 3. vector B bardbl vector B bardbl = correct 4. None of these are true. 5. vector B bardbl vector B bardbl = + 6. vector B bardbl vector B bardbl = + k 7. vector B bardbl vector B bardbl = k 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: 5 . 81956 T. Explanation: Let : r 1 = 79 cm = 0 . 79 m , r 2 = 41 cm = 0 . 41 m , I = 5 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) (5 A) 4 parenleftbigg 1 . 79 m + 1 . 41 m parenrightbigg parenleftbigg 10 6 T 1 T parenrightbigg = ( 5 . 81956 T) bardbl vector B bardbl = 6 . 003 10.0 points Consider two radial legs extending to infinity and a circular arc carrying a current I as shown below. x y I I I I 4 7 O r nguyen (jmn727) oldhomework 21 Turner (59070) 2 What is the magnitude of the magnetic field B O at the origin O due to the current through this path? 1. B O = 3 16 I r 2. B O = 7 48 I r 3. B O = 1 5 I r 4. B O = 1 7 I r correct 5. B O = 0 6. B O = 3 20 I r 7. B O = 1 6 I r 8. B O = 7 40 I r 9. B O = 7 52 I r 10. B O = 7 44 I r Explanation: Using the Biot-Savart law, the magnetic field due to the two radial legs is zero since dvectors r = 0...
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oldhw 21 - nguyen (jmn727) oldhomework 21 Turner (59070) 1...

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