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Unformatted text preview: HPHY 253.02 Exam 01 Spring Semester 2009 Dr. A. E. Bak Name Instructions. For each question, show all work leading to an answer and simplify as much as possible. 1. Measurements indicate that there is an electric &eld surrounding Earth. This &eld has a magnitude of about 150 N= C at Earths surface and points inward toward Earths center. Assume that Earth is a sphere of radius R = 6370 km that carries a uniform surface charge. (a) Is the charge q on Earths surface positive or negative? Explain your answer. (b) Determine q . Note that the electric &eld outside a uniformly charged sphere is the same as if all the charge were concentrated at the spheres center. (c) Determine Earths surface charge density & . 2. An insulating sphere of radius R has a nonuniform volume charge density given by = Ar 2 , where A is a positive constant and the variable r is the distance from the spheres center....
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- Spring '09