Physics21HourExamI-02-06-08

Physics21HourExamI-02-06-08 - Department of Physics, Lehigh...

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1 Department of Physics, Lehigh University Physics 21 – Introductory Physics II Spring 2008 Hour Exam I February 12, 2008 Closed Notes 9:20 AM-10:10 AM Student’s Name______________________ Recitation Section Number______________ Recitation Leader’s Name_______________ The test is a multiple-choice examination. First, check to be sure that you have a six- page examination, including the equation sheet. Please answer each question by circling one answer from the panel of choices available within each question space. 1. (20 points) Four charges Q 1 = Q 4 = q and Q 2 = Q 3 = - 2q are placed on the four corners of a square with side a = 2 cm. Assume that q = 3.20 μC. i and j are the unit vectors along the x- and y- axis, respectively. A. The electrostatic force F 12 on charge Q 1 due to Q 2 is: i) 325 ( i + j ) N; ii) 230 j N; iii) 9.20 i N; iv) 460 i N ; or v) 81.4 (- i + j ) N B. The electrostatic force F 14 on charge Q 1 due to Q 4 is: i) 325 ( i + j ) N; ii) 230 j N ; iii) 9.20 i N; iv) 460 i N; or v) 81.4N (- i + j ) N C. The electrostatic force F 23 on charge Q 2 due to Q 3 is: i) 325 ( i + j ) N; ii) 230 j N; iii) 9.20 i N; iv) 460 i N; or v) 81.4 (- i + j ) N D. Which of the following diagrams best describes the direction of the net force on charge 3? i) ; ii) ; iii) ; iv) ; or v) E. Which of the following diagrams best describes the direction of the net force on charge 4? i) ii) iii) iv) v) i j Q 1 Q 2 Q 3 Q 4 a a
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2 2. (20 points) A semi-circular plastic rod of radius d on an x-y plane has uniform positive charge density of C/m. The center of curvature lies at the origin of the x-y coordinates. A. At the origin, what is the magnitude of the y-component of the electric field due to the semi-circular charge? i) d E y  0 4 1 ; ii) d E y 0 2 1 ; iii) d E y 0 4 1 ; iv) d E y 0 2 1 ; or v) 0 B. At the origin, what is the magnitude of the x-component of the electric field due to the semi-circular charge?
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Physics21HourExamI-02-06-08 - Department of Physics, Lehigh...

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