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Unformatted text preview: Version One – Homework 3 – Savrasov – 39821 – Apr 16, 2007 1 This print-out should have 9 questions. Multiple-choice questions may continue on the next column or page – find all choices before answering. The due time is Central time. Potential Energy and Potential 01 , , , < 1 min, . 001 (part 1 of 1) 1 points Assume we are given an electric field set up by an unknown charge distribution. U is the amount of work needed to bring a point charge of charge q in from infinity to a point P . If the charge q is returned to infinity, how much work would it take to bring a new charge of 4 q from infinity to point P ? 1. 8 U 2. 4 U correct 3. 2 U 4. U 5. U 2 6. U 4 7. U 8 8. 9. More information is needed. 10. The correct answer is not given. Explanation: With the zero of potential energy and elec- tric potential set at zero, the potential V at a point P is V = U q U = V q , where U is the work needed to bring a charge q from infinity to point P . Initially V = U q . To bring a charge of q = 4 q in from infinity requires U = V q = U q 4 q = 4 U . keywords: Equipotential Surfaces 02 25:03, trigonometry, multiple choice, > 1 min, fixed. 002 (part 1 of 2) 1 points Consider the figure + Q #1 + + + + + + + + + + +- Q #2----------- A B C D x y Of the following elements, identify all that correspond to an equipotential line or surface....
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