25 - Kapoor (mk9499) oldhomework 25 Turner (60230) 1 This...

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Unformatted text preview: Kapoor (mk9499) oldhomework 25 Turner (60230) 1 This print-out should have 11 questions. Multiple-choice questions may continue on the next column or page find all choices before answering. 001 (part 1 of 3) 10.0 points Consider the circuit shown. L R R E S P What is the instantaneous current at point P immediately after the switch is closed? 1. I P (0) = 3 E R 2. I P (0) = E 2 R 3. I P (0) = E R L 4. I P (0) = 4 E R 5. I P (0) = 2 E R 6. I P (0) = E R 7. I P (0) = 8 E R 8. I P (0) = E L 2 R 9. I P (0) = 16 E R 10. I P (0) = 0 correct Explanation: The current in L has to change gradually, so immediately after the switch is closed, there is no current going through point P . 002 (part 2 of 3) 10.0 points When the switch has been closed for a long time, what is the energy stored in the induc- tor? 1. U L = L E 2 4 R 2 2. U L = L E 2 2 R 2 correct 3. U L = E 2 R 2 4 L 4. U L = L E 4 R 5. U L = L E 2 R 6. U L = L E 32 R 7. U L = L E 3 R 8. U L = L R 2 2 E 2 9. U L = L E 16 R 10. U L = L E 8 R Explanation: After the switch has been closed for a long time, the current in L does not change any more, so there is no voltage increase nor de- crease across L . Therefore, the current going through L is I = E R , which gives the energy stored in L as U L = 1 2 L I 2 = L E 2 2 R 2 . 003 (part 3 of 3) 10.0 points After the switch has been closed for a long time, it is opened at time t = 0. Which of the following graphs best repre- sents the subsequent current I at point P as a function of time t ? Kapoor (mk9499) oldhomework 25 Turner (60230) 2 1. 0 1 2 3 4 5 6 7 8 910 1 2 3 4 5 Time, t [s] Current, I [A] 2. 0 1 2 3 4 5 6 7 8 910 1 2 3 4 5 Time, t [s] Current, I [A] 3. 0 1 2 3 4 5 6 7 8 910 1 2 3 4 5 Time, t [s] Current, I [A] 4. 0 1 2 3 4 5 6 7 8 910 1 2 3 4 5 Time, t [s] Current, I [A] correct 5. 0 1 2 3 4 5 6 7 8 910 1 2 3 4 5 Time, t [s] Current, I [A] 6....
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This note was uploaded on 06/28/2009 for the course PHY 303L taught by Professor Turner during the Fall '08 term at University of Texas at Austin.

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25 - Kapoor (mk9499) oldhomework 25 Turner (60230) 1 This...

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