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Unformatted text preview: fryer (vdf96) Magnetics 2 Redo graves (6) 1 This printout should have 18 questions. Multiplechoice questions may continue on the next column or page find all choices before answering. 001 10.0 points A vertical electric wire in the wall of a building carries a DC current of 20 A upward. I x S N E S N E (out) What is the magnitude of the magnet field at a point 0 . 1 m due north of this wire? Correct answer: 40 T. Explanation: Let : I = 20 A . The magnetic field due to a current carrying wire at a distance r is B = I 2 r = (4 10 7 T m) (20 A) 2 (0 . 1 m) = 40 T . 002 10.0 points Will a pair of parallel currentcarrying wires exert forces on each other? 1. No; the magnetic field generated by the currents of the wires does not affect the wires themselves. 2. Yes; the magnetic field generated by the current in one wire is perpendicular to the current in the other wire and vise versa. cor rect 3. No; no net magnetic field is generated. 4. No; the two wires attract each other by the magnetic field generated by their currents and repel each other due to the like charges of the moving particles in the wires. The two forces are equal in magnitude. 5. Yes; the wires are electrically charged. Explanation: The magnetic fields generated by the cur rents of the wires are perpendicular to the currents and according to the righthand rule they exert forces on those wires. Both wires are neutral as a whole, so there is no electric force between them. 003 (part 1 of 2) 10.0 points A magnetic field of 0 . 8 T is perpendicular to a square coil of 18 turns. The length of each side of the coil is 4 cm. Find the magnetic flux through an individ ual turn of the coil. Correct answer: 1 . 28 mWb. Explanation: Let : B = 0 . 8 T , N = 18 , = 4 cm = 0 . 04 m , and = 0 . The magnetic flux is = B A cos = B 2 cos = (0 . 8 T) (0 . 04 m) 2 cos 0 10 3 mWb 1 Wb = 1 . 28 mWb . 004 (part 2 of 2) 10.0 points Find the magnetic flux through an individual turn of the coil if the magnetic field makes an angle of 60 with the normal to the plane of the coil. fryer (vdf96) Magnetics 2 Redo graves (6) 2 Correct answer: 0 . 64 mWb. Explanation: Let : = 60 . The magnetic flux is = B A cos = B 2 cos = (0 . 8 T) (0 . 04 m) 2 cos 60 10 3 mWb 1 Wb = . 64 mWb . keywords: 005 (part 1 of 2) 10.0 points A long, straight wire carries a current of 17 . 7 A. An electron travels at 1 . 09 10 5 m / s parallel to the wire, 54 . 5 cm from the wire. The permeability of free space is 1 . 25664 10 6 N / A 2 and the charge on an electron is 1 . 6 10 19 C. What force does the magnetic field of the current exert on the moving electron?...
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This note was uploaded on 12/11/2011 for the course PHYSICS 101 taught by Professor Graves during the Fall '10 term at San Jose City College.
 Fall '10
 Graves
 Physics

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