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Unformatted text preview: Version 006 – TEST01 – TSOI – (92515) 1 This printout should have 11 questions. Multiplechoice questions may continue on the next column or page – find all choices before answering. 001 10.0 points A parallelplate capacitor is made by placing polyethylene ( κ = 2 . 3) between two sheets of aluminum foil. The area of each sheet of aluminum foil is 370 cm 2 , and the thickness of the polyethylene is 0 . 3 mm. The permittivity of free space is 8 . 85 × 10 12 C 2 / N · m 2 . Find the capacitance. 1. 1.04319 2. 3.6639 3. 1.32307 4. 3.05325 5. 1.6284 6. 2.51045 7. 1.66911 8. 3.76568 9. 0.941419 10. 1.07591 Correct answer: 2 . 51045 nF. Explanation: Let : κ = 2 . 3 , = 8 . 85 × 10 12 C 2 / N · m 2 , A = 370 cm 2 = 0 . 037 m 2 , and d = 0 . 3 mm = 0 . 0003 m . The capacitance is C = κ A d = 2 . 3(8 . 85 × 10 12 C 2 / N · m 2 ) (0 . 037 m 2 ) . 0003 m × 10 9 nF F = 2 . 51045 nF . 002 10.0 points Suppose that the strength of the electric field about an isolated point charge has a certain value at a distance of 3 m. How will the electric field strength compare at a distance of 6 m from the point charge? 1. At twice the distance the field strength will be 1 2 of the original value. 2. At twice the distance the field strength will be 1 3 of the original value. 3. At twice the distance the field strength will be twice the original value. 4. At twice the distance the field strength will be the same. 5. At twice the distance the field strength will be 1 4 of the original value. correct Explanation: By the inverse square law, at twice the distance the field strength will be E ∝ 1 (2 r ) 2 = 1 4 r 2 , 1 4 the original strength. 003 10.0 points The two isolated parallel plate capacitors be low, one with plate separation d and the other with D > d , have the same plate area A and are given the same charge Q . 1 2 d D + + ? The energy in the spark produced by dis charging the second capacitor is 1. the same as the discharge spark of the first capacitor. 2. less energetic than the discharge spark of the first capacitor. Version 006 – TEST01 – TSOI – (92515) 2 3. more energetic than the discharge spark of the first capacitor. correct Explanation: The energy of the spark is equal to the potential energy stored in the capacitor. The potential energy of a capacitor is...
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 Summer '08
 morrison
 Physics, Electric charge

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