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Unformatted text preview: montes (dam2772) Homework3 shih (56310) 1 This printout should have 20 questions. Multiplechoice questions may continue on the next column or page find all choices before answering. 001 10.0 points If the emf of a battery is 22 V and a current of 41 A is measured when the battery is shorted, what is the internal resistance of the battery? Correct answer: 0 . 536585 . Explanation: Let : E = 22 V and I = 41 A . When the battery with an emf E is shorted, with current I flowing, the internal resistance R i is R i = E I = 22 V 41 A = . 536585 . 002 10.0 points A length of wire is cut into 7 equal pieces. The 7 pieces are then connected parallel, with the resulting resistance being 5 . What was the resistance r of the original length of wire? Correct answer: 245 . Explanation: Let : n = 7 and R p = 5 . The resulting resistance R p of n equal piece resistors of resistance r connected parallel is R p = r n , but when they are in series, the total resis tance R s is R s = n r = n 2 R p = 7 2 (5 ) = 245 . 003 (part 1 of 4) 10.0 points A typical television dissipates 283 W when plugged into a 116 V outlet. Find the resistance of the television. Correct answer: 47 . 5477 . Explanation: Let : P = 283 W and V = 116 V . Power is P = V 2 R so the television resistance is R TV = V 2 P TV = (116 V) 2 283 W = 47 . 5477 . 004 (part 2 of 4) 10.0 points The 2 . 81 fuse (integrated into the outlet) and wires connecting the outlet form a series circuit that works like a voltage divider. As sume there are no other appliances plugged into the outlet. Find the voltage drop across the television. Correct answer: 109 . 527 V. Explanation: Let : R fuse = 2 . 81 . When the television and a fuse are con nected in series, the total resistance is R tot = R TV + R fuse This combination works like a voltage divider, where V R , so V TV R TV = V tot R tot montes (dam2772) Homework3 shih (56310) 2 V TV = R TV V R TV + R fuse = (47 . 5477 ) 116 V 47 . 5477 + 2 . 81 = 109 . 527 V . 005 (part 3 of 4) 10.0 points A 11 . 4 hair dryer is now plugged into the same outlet. Find the equivalent resistance of the two appliances. (Be sure to consider the TV and the hair dryer only.) Correct answer: 9 . 19533 ....
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This note was uploaded on 03/22/2012 for the course PHYS 302L taught by Professor Tsoi during the Spring '10 term at University of Texas at Austin.
 Spring '10
 TSOI
 Physics, Current, Work

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