PHYS 1051 Midterm: PHYS 1051 Spring 2013 Term Test 3
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Instructions: there are four questions, each worth 12. 5 points in total. Answer all the questions, show all your workings: the amount of points awarded for each part in the bracket next to it, do not erase or whiteout your answers. Draw a line through what you think is wrong and continue your calculations: notes, textbooks, cellphones and electronic devices with exception of a calculator are not permitted, please use three signi cant gures in all calculations, relax. Question i: explain why an electric eld immediately outside a charged conductor in electrostatic equilibrium has only the component perpendicular to the conductor"s surface. [2. 5 points: an insulating sphere of radius 2a is placed inside a conducting shell of inner surface. Rin = 4a and outer surface rout = 6a as shown in the gure below. The total charge on a system (sphere and shell) is determined to be 2q. The electric eld at r = a is e = keq.
