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Unformatted text preview: kavo (ak22862) HW07 Janow (12121) 1 This printout should have 12 questions. Multiplechoice questions may continue on the next column or page find all choices before answering. 001 (part 1 of 2) 10.0 points The potential difference in a simple circuit is 11 V and the resistance is 50 . What current I flows in the circuit? Correct answer: 0 . 22 A. Explanation: Let : V = 11 V and R = 50 . The current is I = V R = 11 V 50 = . 22 A . 002 (part 2 of 2) 10.0 points How many electrons pass a given point in the circuit in 8 min? Correct answer: 6 . 6 10 20 . Explanation: Let : I = 0 . 22 A , t = 8 min = 480 s , and q e = 1 . 6 10 19 C . I = q t , where q is in coulombs and t in seconds; that is, q = I t, and the total charge for n electrons is q = n q e , so n = q q e = I t q e = (0 . 22 A) (480 s) 1 . 6 10 19 C = 6 . 6 10 20 . 003 15.0 points Birds resting on highvoltage power lines are a common sight. The copper wire on which a bird stands is 1 . 25 cm in diameter and carries a current of 136 A. Coppers resistivity is 1 . 68 10 8 m . If the birds feet are 2 . 42 cm apart, what is the potential difference across its body? Correct answer: 450 . 561 V. Explanation: Let : r = 0 . 625 cm = 0 . 00625 m , I = 136 A , L = 2 . 42 cm = 0 . 0242 m , and = 1 . 68 10 8 m . The resistance of the wire between the feet is R = L A so the potential is V = I R = I L A = (136 A) (1 . 68 10 8 m) (0 . 0242 m) (0 . 00625 m) 2 10 6 V V = 450 . 561 V ....
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 Fall '08
 Opyrchal
 Physics

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