ch20-h3-solutions - liu (ql744) ch20-h3 chiu (56565) This...

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This print-out should have 7 questions. Multiple-choice questions may continue on the next column or page – fnd all choices beFore answering. 001 10.0 points A0 . 3 μ ±capacitorisgivenacharge Q 0 .A Fter 2s,thecapacitor’schargeis0 . 5 Q 0 . What is the e²ective resistance across this capacitor? Correct answer: 9 . 61797 MΩ. Explanation: Let : C =0 . 3 μ ±=3 × 10 - 7 ±a n d t =2s . The charge on the capacitor is Q ( t )= Q 0 e - t/τ . e t/τ = Q 0 Q t τ =ln ± Q 0 Q ² τ = t ln ± Q 0 Q ² . The e²ective resistance is R = τ C = t C ln ± Q 0 Q ² = 2s (3 × 10 - 7 ±) ln ± Q 0 0 . 5 Q 0 ² · 1MΩ 10 6 Ω = 9 . 61797 MΩ . 002 (part 1 of 2) 10.0 points A12Vautomobilebatteryisconnectedtoan electric starter motor. The current through the motor is 255 A. How much power does the motor dissipate? Correct answer: 3060 W. Explanation: Power is P = IV =(255A)(12V) = 3060 W . 003 (part 2 of 2) 10.0 points How much energy does the battery deliver to the motor during a 14 . 5speriod? Correct answer: 44370 J. Explanation: Let : V =12V , I =255A , and t =14 .
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This note was uploaded on 10/25/2011 for the course PHY 303L taught by Professor Turner during the Spring '08 term at University of Texas at Austin.

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ch20-h3-solutions - liu (ql744) ch20-h3 chiu (56565) This...

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