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Unformatted text preview: nguyen (jmn727) homework 20 Turner (59070) 1 This printout should have 12 questions. Multiplechoice questions may continue on the next column or page find all choices before answering. 001 10.0 points The electrons in a beam are moving at 2 . 7 10 8 m / s in an electric field of 15000 N / C. What value must the magnetic field have if the electrons pass through the crossed fields undeflected? Correct answer: 55 . 5556 T. Explanation: Let : E = 15000 N / C and v = 2 . 7 10 8 m / s . If the electrons move undeflected through the crossed fields v = E B then B = E v = 15000 N / C 2 . 7 10 8 m / s = 55 . 5556 T . 002 (part 1 of 2) 10.0 points A proton in a cyclotron is moving with a speed of 4 . 67 10 7 m / s in a circle of radius 0 . 728 m. 1 . 67 10 27 kg is the mass of the pro ton, and 1 . 60218 10 19 C is its fundamental charge. What is the magnitude of the force exerted on the proton by the magnetic field of the cyclotron? Correct answer: 5 . 00287 10 12 N. Explanation: Let : v = 4 . 67 10 7 m / s , m p = 1 . 67 10 27 kg , r = 0 . 728 m , and q e = 1 . 60218 10 19 C . The magnetic force is the centripetal force which keeps the proton in circular motion. From the centripetal force equation, we have F = m p v 2 r = (1 . 67 10 27 kg)(4 . 67 10 7 m / s) 2 (0 . 728 m) = 5 . 00287 10 12 N . 003 (part 2 of 2) 10.0 points What is the magnitude of the magnetic field required to keep it moving in this circle? Correct answer: 0 . 668639 T. Explanation: The force is due to the magnetic field. F B = B perp q e v , B = F q e v = . 668639 T . 004 (part 1 of 2) 10.0 points A proton travels with a speed of 3 . 28 10 6 m / s at an angle of 31 . 6 with a magnetic field of . 147 T pointed in the y direction. The charge of proton is 1 . 60218 10 19 C. What is the magnitude of the magnetic force on the proton? Correct answer: 4 . 04782 10 14 N. Explanation: Let : v = 3 . 28 10 6 m / s , = 31 . 6 , and B = 0 . 147 T . F = q v B sin = (1 . 60218 10 19 C)(3 . 28 10 6 m / s) (0 . 147 T) sin31 . 6 = 4 . 04782 10 14 N. nguyen (jmn727) homework 20 Turner (59070) 2 005 (part 2 of 2) 10.0 points The mass of proton is 1 . 67262 10 27...
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This note was uploaded on 01/21/2010 for the course PHY 303L taught by Professor Turner during the Spring '08 term at University of Texas at Austin.
 Spring '08
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