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Unformatted text preview: wilson (kw22588) HW5 Mackie (20224) 1 This printout should have 10 questions. Multiplechoice questions may continue on the next column or page find all choices before answering. 001 10.0 points A charge of 10 . 853 nC is uniformly distributed along the xaxis from 3 m to 3 m. What is the electric potential (relative to zero at infinity) of the point at 5 m on the xaxis? Correct answer: 22 . 537 V. Explanation: Let : x 1 = 3 m , x 2 = 3 m , q = 10 . 853 nC = 1 . 0853 10 8 C , and k e = 8 . 98755 10 9 N m 2 / C 2 . The equation for the electric potential with the reference at is V = k e integraldisplay d q r . Since the charge is uniformly distributed along the x axis, the linear charge density is simply = q L , where L is the length of the line of charge. Hence d q = d x = q L d x . Further, the distance from the point 5 m on the x axis to a charge element is r = 5 x . Thus V = k e q L integraldisplay x 2 x 1 d x 5 x = k e q L ln parenleftbigg 5 x 1 5 x 2 parenrightbigg = 8 . 98755 10 9 N m 2 / C 2 1 . 0853 10 8 C 3 m ( 3 m) ln parenleftbigg 5 m ( 3 m) 5 m 3 m parenrightbigg = 22 . 537 V . 002 10.0 points The uniformly charged sphere gives a reason able model of the proton charge distribution in an atomic nucleus. A nucleus of lead208 has a radius of 5 . 582 10 15 m and contains 82 protons, each with a charge of 1 . 6 10 19 C. Calculate the electric potential at the sur face of this nucleus. Correct answer: 2 . 11244 10 7 V. Explanation: Let : r = 5 . 582 10 15 m , e = 1 . 6 10 19 C , Z = 82 , and k e = 8 . 98755 10 9 N m 2 / C 2 ....
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This note was uploaded on 02/17/2011 for the course PHY 303L taught by Professor Turner during the Spring '08 term at University of Texas at Austin.
 Spring '08
 Turner
 Physics, Charge

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