HW 18 - terry (ect328) homework 18 Turner (59130) This...

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terry (ect328) – homework 18 – Turner – (59130) 1 This print-out should have 9 questions. Multiple-choice questions may continue on the next column or page – fnd all choices beFore answering. 001 10.0 points An air-flled cylindrical capacitor has a capac- itance oF 15 p± and is 6 . 7 cm in length. The coulomb constant is 8 . 98755 × 10 9 N · m 2 / C 2 . IF the radius oF the outside conductor is 0 . 7 cm, what is the required radius oF the inner conductor? Correct answer: 0 . 545983 cm. Explanation: Let : k e = 8 . 98755 × 10 9 N · m 2 / C 2 , = 6 . 7 cm = 0 . 067 m , b = 0 . 7 cm , and C = 15 p± = 1 . 5 × 10 11 ± . The capacitance oF a cylindrical capacitor is given by C = 2 k e ln b a where a and b are the inner and outer radii, respectively. Solving For a , we obtain a = b e ℓ/ (2 k e C ) = (0 . 7 cm) e (0 . 067 m) / [2 k e (1 . 5 × 10 - 11 F)] = 0 . 545983 cm . 002 10.0 points IF the plate separation oF an isolated parallel plate capacitor is doubled, 1. the potential di²erence is halved. 2. the electric feld is doubled. 3. the charge on the each plate is halved. 4. the charge density on each plate is dou- bled. 5. None oF these correct Explanation: Q and A are constant, so E = Q A ǫ 0 = constant so that E = 2 Q 2 A ǫ 0 and V = Q C = 2 Q C = 2 Q C = 2 V . 003 (part 1 oF 2) 10.0 points Consider the system oF capacitors connected to a battery as shown below. E B 3 μ ± 3 μ ± 3 μ ± 3 μ ± 3 μ ± 3 μ ± ±ind the equivalent capacitance oF the cir- cuit. 1. C = 3 2 μ ± 2. C = 3 μ ± 3. C = 4 μ ± 4. C = 2 3 μ ± 5. C = 1 μ ± 6. C = 2 μ ± correct 7. C = 4 3 μ ± Explanation:
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This note was uploaded on 02/17/2010 for the course PHY 59130 taught by Professor Turner during the Fall '09 term at University of Texas.

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HW 18 - terry (ect328) homework 18 Turner (59130) This...

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