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Unformatted text preview: PHYS 2212 Test 2 Oct 13th 2010 Name (print) Instructions • Read all problems carefully before attempting to solve them. • Your work must be legible, and the organization must be clear. • You must show all work, including correct vector notation. • Correct answers without adequate explanation will be counted wrong. • Incorrect work or explanations mixed in with correct work will be counted wrong. Cross out anything you don’t want us to read! • Make explanations correct but brief. You do not need to write a lot of prose. • Include diagrams! • Show what goes into a calculation, not just the final number, e.g.: a · b c · d = (8 × 10 3 )(5 × 10 6 ) (2 × 10 5 )(4 × 10 4 ) = 5 × 10 4 • Give standard SI units with your results. Unless specifically asked to derive a result, you may start from the formulas given on the formula sheet, including equations corresponding to the fundamental concepts. If a formula you need is not given, you must derive it. If you cannot do some portion of a problem, invent a symbol for the quantity you can’t calculate (explain that you are doing this), and use it to do the rest of the problem. Honor Pledge “In accordance with the Georgia Tech Honor Code, I have neither given nor received unauthorized aid on this test.” Sign your name on the line above PHYS 2212 Do not write on this page! Problem Score Grader Problem 1 (30 pts) Problem 2 (20 pts) Problem 3 (25 pts) Problem 4 (25 pts) Problem 1 (30 Points) A solid circular glass cylinder has a radius R and length L . The axis of the cylinder lies along the x axis, with the left end at the origin (see figure). A net positive charge + Q is distributed uniformly throughout the cylinder’s volume. Calculate the net electric field vector E at observation location w by answering the following sequence of questions: (a 5pts) Consider a diskshaped slice of the cylinder of thickness dx that is a distance x from the left end of the cylinder. Find the position vector vector r that points from center of this slice to the observation location w . (b 5pts) Determine the expression for the charge, dQ , in terms of the disk thickness dx and relevant known variables. (c 10pts) Derive an expression for d vector E , the electric field of the disk at the observation location w . Note that d vector E depends on  vector r  , the distance from the observation location w to the disk; however, you may assume that  vector r  is small compared to the disk’s radius R . (Hint: the following expression copied directly from the formula sheet may prove to be useful:  vector E disk  ≈ Q/A 2 ǫ [1 − z R ].) (d 10pts) Integrate over the charge distribution to determine the electric field vector E at observation location w . Problem 2 (20 Points)...
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This note was uploaded on 05/23/2011 for the course PHYISCS 2212 taught by Professor Shatz during the Spring '10 term at Georgia Tech.
 Spring '10
 SHATZ

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