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Unformatted text preview: Version 035 Midterm2 li (59050) 1 This printout should have 16 questions. Multiplechoice questions may continue on the next column or page find all choices before answering. 001 10.0 points The current in a circuit is tripled by connect ing a 717 resistor parallel with the resis tance of the circuit. Determine the resistance of the circuit in the absence of the 717 resistor. 1. 824.0 2. 1252.0 3. 920.0 4. 682.0 5. 1074.0 6. 510.0 7. 1364.0 8. 590.0 9. 766.0 10. 1434.0 Correct answer: 1434 . Explanation: Let : R 1 = 717 . If the initial resistance is R and the added resistance is R 1 we have 3 R = 1 R + 1 R 1 2 R = 1 R 1 R = 2 R 1 = 2(717 ) = 1434 . 002 10.0 points Which of the following capacitors, each of which has plates of area A , would store the most charge on the top plate for a given po tential difference V ? 1. b V d Glass 2. b V d/ 2 Air 3. b V d/ 2 Vacuum 4. b V d Vacuum 5. b V d/ 2 Glass correct Explanation: The problem actually asks which capacitor has the largest capacitance, since, Q = C V . The capacitance for the parallel plate capaci tor is C = o A d , so the largest and small est distance gives the largest capacitance. Glass, being a dielectric material, has > 1, where the dielectric constant of air is 1. Therefore, the capacitor with the plate dis tance d 2 and glass between plates has highest capacitance. 003 10.0 points Consider the capacitor circuit Version 035 Midterm2 li (59050) 2 E B 9 F 2 F 8 F 3 F b a c Calculate the equivalent capacitance C ab between points a and b . 1. 3.42857 2. 4.73684 3. 4.44444 4. 3.75 5. 4.8 6. 5.5 7. 5.14286 8. 4.5 9. 4.63158 10. 5.0 Correct answer: 5 . 5 F. Explanation: Let : C 1 = 9 F , C 2 = 8 F , C 3 = 2 F , and C 4 = 3 F . E B C 1 C 3 C 2 C 4 b a c For capacitors in series, 1 C series = summationdisplay 1 C i V series = summationdisplay V i , and the individual charges are the same. For parallel capacitors, C parallel = summationdisplay C i Q parallel = summationdisplay Q i , and the individual voltages are the same. Let c be the point between the two parallel sections. Let c be the point between the two parallel sections. The capacitance between a an c is C l = C 1 + C 3 = 9 F + 2 F = 11 F . The capacitance between b and c is C r = C 2 + C 4 = 8 F + 3 F = 11 F . Thus the capacitance between a and b is 1 C ab = 1 C l + 1 C r = C r + C l C l C r C ab = C l C r C l + C r = (11 F) (11 F) 11 F + 11 F = 5 . 5 F . 004 10.0 points 3 . 6 2 . 6 12 . 4 15 . 6 V 7 . 8 V Find the current through the 12 . 4 lower right resistor. 1. 0.836735 2. 1.32632 3. 0.875912 4. 1.30088 5. 1.24419 Version 035 Midterm2 li (59050) 3 6. 1.0292 7. 1.36047 8. 0.481707 9. 0.784 10. 0.795918 Correct answer: 0 . 795918 A....
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 Spring '08
 Turner
 Physics, Current

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