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Unformatted text preview: duong (ktd359) Homework 2 Spurlock (44203) 1 This print-out should have 81 questions. Multiple-choice questions may continue on the next column or page find all choices before answering. 001 10.0 points You have a potential difference of 11 V. How much work is done to transfer 0 . 22 C of charge through it? Correct answer: 2 . 42 J. Explanation: Let : V = 11 V and q = 0 . 22 C . The potential difference is V = W q W = V q = (11 V) (0 . 22 C) = 2 . 42 J . 002 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. 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 . 003 10.0 points An ion accelerated through a potential dif- ference of 137 V experiences an increase in kinetic energy of 5 . 92 10 17 J. Find the magnitude of the charge on the ion. Correct answer: 4 . 32117 10 19 C. Explanation: Let : V = 137 V and K = 5 . 92 10 17 J . By conservation of energy K = q V q = K V = 5 . 92 10 17 J 137 V = 4 . 32117 10 19 C , which has a magnitude of 4 . 32117 10 19 C . 004 10.0 points Points A (1 m, 2 m) and B (3 m, 4 m) are in a region where the electric field is uniform and given by vector E = E x + E y , where E x = 4 N / C and E y = 4 N / C. What is the potential difference V A V B ? Correct answer: 16 V. Explanation: Let : E x = 4 N / C , E y = 4 N / C , ( x A , y A ) = (1 m , 2 m) , and ( x B , y B ) = (3 m , 4 m) . We know V ( A ) V ( B ) = integraldisplay A B vector E dvectors = integraldisplay B A vector E dvectors For a uniform electric field vector E = E x + E y . duong (ktd359) Homework 2 Spurlock (44203) 2 Now consider the term E x dvectors in the inte- grand. E x is just a constant and dvectors may be interpreted as the projection of dvectors onto x , so that E x dvectors = E x dx . Likewise E y dvectors = E y dy . Or more simply, dvectors = dx + dy dotting it with E x + E y gives the same result as above. Therefore V A V B = E x integraldisplay x B x A dx + E y integraldisplay y B y A dy = (4 N / C) (3 m 1 m) + (4 N / C) (4 m 2 m) = 16 V . Note that the potential difference is inde- pendent of the path taken from A to B. 005 (part 1 of 2) 10.0 points k e = 8 . 98755 10 9 N m 2 / C 2 , and the charge on a proton is 1 . 60218 10 19 C . Find the potential 1 . 05 cm from a proton....
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- Spring '08