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Unformatted text preview: terry (ect328) oldhomework 26 Turner (59130) 1 This printout should have 14 questions. Multiplechoice questions may continue on the next column or page find all choices before answering. 001 10.0 points In an RL series circuit, an inductor of 4 . 26 H and a resistor of 6 . 45 are connected to a 28 . 4 V battery. The switch of the circuit is initially open. Next close the switch and wait for a long time. Eventually the current reaches its equilibrium value. At this time, what is the corresponding energy stored in the inductor? Correct answer: 41 . 2949 J. Explanation: Let : L = 4 . 26 H , R = 6 . 45 , and E = 28 . 4 V . The current in an RL circuit is I = E R parenleftBig 1 e Rt/L parenrightBig . The final equilibrium value of the current, which occurs as t , is I = E R = 28 . 4 V 6 . 45 = 4 . 4031 A . The energy stored in the inductor carrying a current 4 . 4031 A is U = 1 2 L I 2 = 1 2 (4 . 26 H) (4 . 4031 A) 2 = 41 . 2949 J . 002 (part 1 of 3) 10.0 points A long solenoid carries a current I 2 . Another coil (of larger diameter than the solenoid) is coaxial with the center of the solenoid, as in the figure below. 2 1 Outside solenoid has N 1 turns Inside solenoid has N 2 turns A 1 A 2 The current I 2 is held constant. The energy stored in the solenoid is given by 1. U = 2 N 2 2 2 A 2 I 2 2 2. U = 2 A 2 2 I 2 3. U = 2 N 2 A 2 2 I 2 2 4. U = 2 N 2 2 A 1 2 I 2 2 5. U = 2 N 2 2 A 2 I 2 2 6. U = 2 N 2 2 A 2 2 I 2 2 correct 7. U = 2 N 2 2 A 2 2 I 2 8. U = 1 2 N 2 2 A 2 I 2 2 Explanation: The magnetic energy density is given by B 2 2 . Inside the solenoid the magnetic field is B = N 2 I 2 2 , and the volume enclosed by the solenoid is A 2 2 , so U = 1 2 parenleftbigg N 2 2 I 2 parenrightbigg 2 A 2 2 = 2 N 2 2 A 2 2 I 2 2 . 003 (part 2 of 3) 10.0 points The mutual inductance M 12 between the coil and the solenoid is given by terry (ect328) oldhomework 26 Turner (59130) 2 1. M 12 = N 1 N 2 A 2 2 correct 2. M 12 = N 1 N 2 A 1 2 3. M 12 = N 1 N 1 N 2 4. M 12 = N 1 N 2 A 1 5. M 12 = N 2 A 2 2 6. M 12 = 2 N 1 N 2 A 2 7. M 12 = N 1 N 2 2 Explanation: The mutual inductance M 12 of loop 1 with respect to loop 2 is defined as M 12 N 1 12 I 2 , where 12 is the flux through a single loop 1 due to loop 2. Since the magnetic field insidedue to loop 2....
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This note was uploaded on 02/17/2010 for the course PHY 59130 taught by Professor Turner during the Fall '09 term at University of Texas at Austin.
 Fall '09
 Turner

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