9 - Kapoor(mk9499 – oldhomework 09 – Turner –(60230 1...

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Unformatted text preview: Kapoor (mk9499) – oldhomework 09 – Turner – (60230) 1 This print-out should have 12 questions. Multiple-choice questions may continue on the next column or page – find all choices before answering. 001 (part 1 of 2) 10.0 points Two spherical conductors (shown in the fig- ure below) are separated by a distance large enough to make induction effects negligible. The spheres (with radii 15 cm and 9 cm) are connected by a thin conducting wire and are brought to the same potential of 775 V rela- tive to 0 V at r = ∞ . 15 cm 9 cm Q 1 Q 2 Determine the capacitance of the sys- tem. The Coulomb constant is 8 . 98755 × 10 9 N · m 2 / C 2 . Correct answer: 2 . 67036 × 10 − 11 F. Explanation: Let : k e = 8 . 98755 × 10 9 N · m 2 / C 2 , R 1 = 15 cm = 0 . 15 m , and R 2 = 9 cm = 0 . 09 m . R 1 R 2 Q 1 Q 2 Both spherical conductors are at the same potential V , so V = k e Q 1 R 1 = k e Q 2 R 2 . The charges on the spheres are then Q 1 = V R 1 k e and Q 2 = V R 2 k e . The capacitance of the system is C = Q 1 + Q 2 V = R 1 + R 2 k e = . 15 m + 0 . 09 m 8 . 98755 × 10 9 N · m 2 / C 2 = 2 . 67036 × 10 − 11 F . 002 (part 2 of 2) 10.0 points What is the charge ratio Q 1 Q 2 ? Correct answer: 1 . 66667. Explanation: From Eq. 2, Q ∝ R , so we have Q 1 Q 2 = R 1 R 2 = 15 cm 9 cm = 1 . 66667 . 003 10.0 points A parallel plate capacitor is connected to a battery. + Q- Q d b b 2 d b b If we double the plate separation, 1. the potential difference is halved....
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This note was uploaded on 06/28/2009 for the course PHY 303L taught by Professor Turner during the Fall '08 term at University of Texas.

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9 - Kapoor(mk9499 – oldhomework 09 – Turner –(60230 1...

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