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Unformatted text preview: fullwood (tf5349) Homework 2 Electric Field and Potential Catala (12054) 1 This printout should have 20 questions. Multiplechoice questions may continue on the next column or page find all choices before answering. 001 10.0 points A positron (a particle with a charge of + e and a mass equal to that of an electron) that is accelerated from rest between two points at a fixed potential difference acquires a speed of 9 . 3 10 7 m / s. What speed is achieved by a proton acceler ated from rest between the same two points? (Disregard relativistic effects.) Correct answer: 2 . 17005 10 6 m / s. Explanation: Let : v f,positron = 9 . 3 10 7 m / s , m positron = 9 . 109 10 31 kg , m pr = 1 . 673 10 27 kg , and q pr = q positron = 1 . 60 10 19 C . Since K i = 0 J , K f = U 1 2 mv 2 f = q V . V = m positron ( v f,positron ) 2 2 q positron = (9 . 109 10 31 kg) (9 . 3 10 7 m / s) 2 2 (1 . 60 10 19 C) = 24619 . 9 V . Thus v f,pr = radicalBigg 2 U electric m pr = radicalBigg 2 ( q pr V ) m pr = radicalBigg 2 (1 . 60 10 19 C) (24619 . 9 V) 1 . 673 10 27 kg = 2 . 17005 10 6 m / s . 002 (part 1 of 2) 10.0 points An electric field does 9 J of work on a 0 . 0009 C charge. What is the voltage change? Correct answer: 10000 V. Explanation: Let : W = 9 J and q = 0 . 0009 C . Work is W = qV V = W q = 9 J . 0009 C = 10000 V . 003 (part 2 of 2) 10.0 points The same electric field does 18 J of work on a . 0018 C charge. What is the voltage change? Correct answer: 10000 V. Explanation: Let : W = 18 J and q = 0 . 0018 C . The voltage change is V = W q = 18 J . 0018 C = 10000 V . 004 10.0 points The magnitude of a uniform electric field be tween the two plates is about 2 10 5 N / C. If the distance between these plates is . 1 cm, find the potential difference between the plates. Correct answer: 200 V. fullwood (tf5349) Homework 2 Electric Field and Potential Catala (12054) 2 Explanation: Let : E = 2 10 5 N / C and d = 0 . 1 cm = 0 . 001 m . The magnitude of the potential difference is V = E d = (2 10 5 N / C) (0 . 001 m) = 200 V . 005 10.0 points The Coulomb constant is 8 . 98755 10 9 N m 2 / C 2 and the acceleration of gravity is 9 . 81 m / s 2 ....
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This note was uploaded on 06/10/2010 for the course PHY 100 taught by Professor Pro.kiroshima during the Spring '10 term at Adelphi.
 Spring '10
 PRO.KIROSHIMA
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