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Unformatted text preview: Prelim2 Practice Answer Key 1. true or false • F, it has to be vector sum. • F, Gauss’ Law gives the net electric field. • F, think about an electron moving inside a capacitor with initial velocity perpendicular to the ~ E field. • F, the flux remains constant. • T • F, the electric potential is constant but not necessarily zero. • F, the charges are on the inner surfaces. • F, with the voltage unchanged and the capacitance decreased, the total charge decreases. • F, the battery near the end of its useful life has the same emf, but a much larger internal resistance. • F, the parallel case has larger power. • T • F, only true if the electric field is uniform. • T 2. C, the two spheres will be at equal potential if connected by a wire. 3. C, 4. C, A, C 5. C, C, B, A (the capacitor has to do work so that the energy stored in it will decrease.) 6. see graphs at the end 7. (a) Inner: -Q, Outer: +2Q, (b) The electric field E ( r ) = Q 2 π r 2 , r > 3 R E ( r ) = Q...
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