SAMPLEFinalExamSolutions

SAMPLEFinalExamSolutions - ID: A UCSD Physics 2B Answer...

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ID: A 1 UCSD Physics 2B Summer Session SAMPLE Final Exam Answer Section MULTIPLE CHOICE 1. ANS: C F = k q 1 q 2 r 2 = 9.0 × 10 9 Nm 2 / C 2 Ê Ë Á Á Á ˆ ¯ ˜ ˜ ˜ 45.0 × 9 C Ê Ë Á Á Á ˆ ¯ ˜ ˜ ˜ 63.0 × 9 C Ê Ë Á Á Á ˆ ¯ ˜ ˜ ˜ 25.0 × 3 m Ê Ë Á Á Á ˆ ¯ ˜ ˜ ˜ 2 = 4.08 × 2 N PTS: 1 2. ANS: E # e = 410 × 9 C Ê Ë Á Á Á ˆ ¯ ˜ ˜ ˜ 1 e + 1.60 × 19 C Ê Ë Á Á Á ˆ ¯ ˜ ˜ ˜ = 2.56 × + 12 PTS: 1 3. ANS: B By definition E = F q = 1200 N 23 × 3 C = 5.2 × 4 N C PTS: 1 4. ANS: A The absolute potential at distance r from a point charge q is V = k q r which varies inversely (not inverse square) with distance PTS: 1 5. ANS: A Capacitors in parallel add C PAR = C 1 + C 2 + ë PTS: 1 6. ANS: B Resistors in parallel obey the formula 1 R = 1 R 1 + 1 R 2 + ë and, when all N resistors have the same value, R = 1 N R PTS: 1
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ID: A 2 7. ANS: C Current is equal to charge per unit time, but we must convert electron charge into Coulombs I = Q t = 475 × 10 16 e 1min 1.6 × 19 C 1e Ê Ë Á Á Á Á Á Á Á Á ˆ ¯ ˜ ˜ ˜ ˜ ˜ ˜ ˜ ˜ 1min 60sec Ê Ë Á Á Á Á Á Á ˆ ¯ ˜ ˜ ˜ ˜ ˜ ˜ = 1.27 × 2 A = 12.7m A PTS: 1 8. ANS: C By definition J = I Area = I π R 2 = 12 A 3.6 × 2 m Ê Ë Á Á Á ˆ ¯ ˜ ˜ ˜ 2 = 2.9 × 2 A m 2 PTS: 1 9. ANS: B R = V I = 210 V 10.5 A = 20 Ω PTS: 1 10. ANS: A E = P × t = V × I × t = 12.0 J C Ê Ë Á Á Á Á Á Á ˆ ¯ ˜ ˜ ˜ ˜ ˜ ˜ 52.0 C s Ê Ë Á Á Á Á Á Á ˆ ¯ ˜ ˜ ˜ ˜ ˜ ˜ 90 sec () = 56.2 kJ PTS: 1 11. ANS: D The field at the center of a current loop is B = μ 0 I 2 R I = BD 0 = 3.28 × 4 T Ê Ë Á Á Á ˆ ¯ ˜ ˜ ˜ 17.0 × 3 m Ê Ë Á Á Á ˆ ¯ ˜ ˜ ˜ 1.26 × 6 H / m Ê Ë Á Á Á ˆ ¯ ˜ ˜ ˜ = 4.43 A PTS: 1 12. ANS: D emf = d Φ dt = NBA T so emf is inversely proportional to period. PTS: 1 13. ANS: B V peak = 2 V rms = 2 440 V = 622 V PTS: 1 14. ANS: B V P V S = N P N S V S = V P N s N p = 2500 V 18,000 300 Ê Ë Á Á Á Á Á Á ˆ ¯ ˜ ˜ ˜ ˜ ˜ ˜ = 150,000 V PTS: 1
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ID: A 3 15. ANS: D ω = 1 LC = 1 0.370 × 10 3 H Ê Ë Á Á Á ˆ ¯ ˜ ˜ ˜ 0.260 × 3 F Ê Ë Á Á Á ˆ ¯ ˜ ˜ ˜ = 3.22 × 3 rad/sec PTS: 1 16. ANS: A τ = RC = 160 Ω () 55 × 3 F Ê Ë Á Á Á ˆ ¯ ˜ ˜ ˜ = 8.8 s PTS: 1 17. ANS: E emf =− L dI dt 6.5 H 50 A / s = 325 V = 0.33 kV PTS: 1 18. ANS: E Definition PTS: 1 19. ANS: A Definition PTS: 1 NUMERIC RESPONSE 1. ANS: U = 1 2 CV 2 = 1 2 3.0 × 6 C Ê Ë Á Á Á ˆ ¯ ˜ ˜ ˜ 5.0 × 3 V Ê Ë Á Á Á ˆ ¯ ˜ ˜ ˜ 2 = 37.5 J PTS: 1 2. ANS: This circuit can be reduced to two series capacitors. The two in parallel add, to give
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SAMPLEFinalExamSolutions - ID: A UCSD Physics 2B Answer...

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