fall_05_exam1_sol_phy2049

# fall_05_exam1_sol_phy2049 - PHY2049 Fall 2005 Prof. Andrew...

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PHY2049 Fall 2005 1 Prof. Andrew Rinzler Prof. Paul Avery Sep. 26, 2005 PHY2049, Fall 2005 Exam 1 Solutions 1. Two identical conducting spheres A and B carry identical charges. They are separated by a distance much larger than their diameters. A third identical conducting sphere C is uncharged. Sphere C is first touched to A, then to B and finally removed. As a result, the electrostatic force between A and B, initially F , becomes (1) 3 F /8 (2) F (3) F /2 (4) F /16 (5) 0 Let the initial charge on A and B be called Q. When C is touched to A, because they are identical they each half the total charge or Q/2. Similarly, when C is then touched to B, they each get half the total charge or 3Q/4. Since A and B now have charges Q/2 and 3Q/4, respectively, the force between them becomes 3/8 of its initial value. 2. Two charged point particles are located at two vertices of an equilateral triangle and the electric field is zero at the third vertex. We conclude (1) at least one other charge is present (2) the two particles have charges with opposite signs and the same magnitude (3) the two particles have charges with opposite signs and different magnitudes (4) the two particles have identical charges (5) the two particles have charges with the same sign and different magnitudes When only two charges are present, the electric field at the third vertex cannot be zero,

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## This test prep was uploaded on 04/17/2008 for the course PHY 2054 taught by Professor Avery during the Spring '08 term at University of Florida.

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fall_05_exam1_sol_phy2049 - PHY2049 Fall 2005 Prof. Andrew...

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