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Unformatted text preview: rosen (arr956) Homework 06 Chiu (58295) 1 This printout should have 23 questions. Multiplechoice questions may continue on the next column or page find all choices before answering. 001 (part 1 of 2) 10.0 points A battery with an emf of 13 V and internal resistance of 0 . 43 is connected across a load resistor R . If the current in the circuit is 2 . 16 A, what is the value of R ? Correct answer: 5 . 58852 . Explanation: Let : E = 13 V , I = 2 . 16 A , and R i = 0 . 43 . The electromotive force E is given by E = I ( R + R i ) R = E I R i = 13 V 2 . 16 A . 43 = 5 . 58852 . 002 (part 2 of 2) 10.0 points What power is dissipated in the internal re sistance of the battery? Correct answer: 2 . 00621 W. Explanation: The power dissipation due to the internal resistance is P = I 2 R i = (2 . 16 A) 2 (0 . 43 ) = 2 . 00621 W . 003 (part 1 of 2) 10.0 points Four resistors are connected as shown in the figure. 92 V S 1 c d a b 1 7 42 52 8 2 Find the resistance between points a and b . Correct answer: 12 . 2464 . Explanation: E B S 1 c d a b R 1 R 2 R 3 R 4 Let : R 1 = 17 , R 2 = 42 , R 3 = 52 , R 4 = 82 , and E = 92 V . Ohms law is V = I R . A good rule of thumb is to eliminate junc tions connected by zero resistance. E B a d b c R 1 R 2 R 3 R 4 rosen (arr956) Homework 06 Chiu (58295) 2 The series connection of R 2 and R 3 gives the equivalent resistance R 23 = R 2 + R 3 = 42 + 52 = 94 . The total resistance R ab between a and b can be obtained by calculating the resistance in the parallel combination of the resistors R 1 , R 4 , and R 23 ; i.e. , 1 R ab = 1 R 1 + 1 R 2 + R 3 + 1 R 4 = R 4 ( R 2 + R 3 ) + R 1 R 4 + R 1 ( R 2 + R 3 ) R 1 R 4 ( R 2 + R 3 ) R ab = R 1 R 4 ( R 2 + R 3 ) R 4 ( R 2 + R 3 ) + R 1 R 4 + R 1 ( R 2 + R 3 ) The denominator is R 4 ( R 2 + R 3 ) + R 1 R 4 + R 1 ( R 2 + R 3 ) = (82 )[42 + 52 ] + (17 ) (82 ) + (17 ) [42 + 52 ] = 10700 2 , so the equivalent resistance is R ab = (17 ) (82 ) [42 + 52 ] (10700 2 ) = 12 . 2464 . 004 (part 2 of 2) 10.0 points What is the current in the 42 resistor? Correct answer: 0 . 978723 A. Explanation: The voltages across R 2 and R 3 , respec tively, (the voltage between a and b ) are V ab = V 23 = 92 V , and we have I 23 = I 3 = I 2 = V ab R 23 = 92 V 94 = . 978723 A . 005 10.0 points The following diagram shows a closed elec trical circuit. The ammeter in the center of the resistive network reads zero amperes. E S 1 A 4 6 6 R x Find the electric resistance R X . 1. R X = 9 . correct 2. R X = 12 . 3. R X = 21 . 4. R X = 18 . 5. R X = 4 . 6. R X = 7 . 7. R X = 24 ....
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This note was uploaded on 04/13/2009 for the course PHY 303L taught by Professor Turner during the Spring '08 term at University of Texas at Austin.
 Spring '08
 Turner
 Physics, Work

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