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UnitExam5Asolutions

# UnitExam5Asolutions - ID A UCSD Physics 2B Answer Section...

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ID: A 1 UCSD Physics 2B Unit Exam 5A AC Circuits Answer Section MULTIPLE CHOICE 1. ANS: D V t ( ) = V P sin ω t ( ) V P = V t ( ) sin ω t ( ) = 122 V sin 314 rad / s ( ) 0.153 s ( ) Ï Ì Ó Ô Ô Ô ¸ ˝ ˛ Ô Ô Ô = 154 V TOP: AC VOLTAGE 2. ANS: A Flux through a solenoid Φ = NBA = N μ 0 I N length Ê Ë Á Á Á Á Á Á ˆ ¯ ˜ ˜ ˜ ˜ ˜ ˜ π R 2 Ê Ë Á Á Á ˆ ¯ ˜ ˜ ˜ = μ 0 N 2 π R 2 I length Self-inductance L = Φ I = μ 0 N 2 π R 2 length N = L R 2 length μ 0 π N = 6.00 H 10.0 × 10 2 m Ê Ë Á Á Á ˆ ¯ ˜ ˜ ˜ 2 20.1 × 10 2 m 1.26 × 10 6 H / m Ê Ë Á Á Á ˆ ¯ ˜ ˜ ˜ 3.14 ( ) = 5520 Answer is rounded to 3 sig figs TOP: SELF-INDUCTANCE 3. ANS: E V rms = 1 2 V peak = 0.707 ( ) 375 V ( ) = 265 V TOP: RMS 4. ANS: C As t → ∞ , the field in the inductor becomes saturated and there is no "back emf". Hence, the inductor acts like a short circuit and only R 1 is left. We then have I = V R 1 = 90 V 150 Ω = 6.0 × 10 1 A = 600m A TOP: RC CIRCUIT CONCEPT 5. ANS: B emf = − d Φ dt = − d dt NBA × cos ω t ( ) = NBA × ω sin ω t ( ) V peak = max emf Ê Ë Á ˆ ¯ ˜ = NBA ω = NBA 2 π f

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UnitExam5Asolutions - ID A UCSD Physics 2B Answer Section...

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