20-3 - brown (twb493) – ch20-h3 – chiu – (56565) 1...

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Unformatted text preview: brown (twb493) – ch20-h3 – chiu – (56565) 1 This print-out should have 7 questions. Multiple-choice questions may continue on the next column or page – find all choices before answering. 001 10.0 points A 0 . 19 μ F capacitor is given a charge Q . After 1 s, the capacitor’s charge is 0 . 5 Q . What is the effective resistance across this capacitor? Correct answer: 7 . 59313 MΩ. Explanation: Let : C = 0 . 19 μ F = 1 . 9 × 10- 7 F and t = 1 s . The charge on the capacitor is Q ( t ) = Q e- t/τ . e t/τ = Q Q t τ = ln parenleftbigg Q Q parenrightbigg τ = t ln parenleftbigg Q Q parenrightbigg . The effective resistance is R = τ C = t C ln parenleftbigg Q Q parenrightbigg = 1 s (1 . 9 × 10- 7 F) ln parenleftbigg Q . 5 Q parenrightbigg · 1 MΩ 10 6 Ω = 7 . 59313 MΩ . 002 (part 1 of 2) 10.0 points A 12 V automobile battery is connected to an electric starter motor. The current through the motor is 223 A....
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This note was uploaded on 12/01/2011 for the course PHY 303L taught by Professor Turner during the Fall '08 term at University of Texas.

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20-3 - brown (twb493) – ch20-h3 – chiu – (56565) 1...

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