HW #8-solutions - nanni (arn437) HW #8 Erskine (56905) 1...

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Unformatted text preview: nanni (arn437) HW #8 Erskine (56905) 1 This print-out should have 21 questions. Multiple-choice questions may continue on the next column or page find all choices before answering. 001 (part 1 of 2) 10.0 points The output of a generator is given by V = V max sin t. If after 0 . 0134 s , the output is 0 . 25 times V max , what is the largest possible angular velocity of the generator? Correct answer: 18 . 8567 rad / s. Explanation: Let : V = 0 . 25 V max , and t 1 = 0 . 0134 s . (0 . 25) V max = V max sin( t 1 ) t 1 = sin 1 (0 . 25) . So the largest possible angular velocity is = sin 1 (0 . 25) t 1 = sin 1 (0 . 25) . 0134 s = 18 . 8567 rad / s , since there are an infinite number of higher harmonics. 002 (part 2 of 2) 10.0 points What is the next time (value of t ) for which the output is 0 . 25 times V max ? Correct answer: 0 . 153203 s. Explanation: V max t 1 t 2 t 1 T 2 From the figure, we see that the next value of t for which V = (0 . 25) V max occurs at t 2 = T 2- t 1 , where T is the period. The frequency is given by f = 2 , and the period by T = 1 f = 2 , so the required time is t 2 = T 2- t 1 = - t 1 = 18 . 8567 rad / s- . 0134 s = . 153203 s . Note: The third time for which the output is 0 . 25 times V max is simply t 3 = t 1 + T , where T is the period. 003 10.0 points The graph below depicts an oscillating emf . E max E min T/ 2 T Which phasor diagram correctly represents this oscillation? Assume counter-clockwise rotation. 1. E 2. E nanni (arn437) HW #8 Erskine (56905) 2 3. E 4. E 5. E correct Explanation: The oscillating emf is proportional to sin( t- ). So the right answer is E 004 (part 1 of 3) 10.0 points An AC voltage of the form V = V max sin2 ft, with frequency 72 Hz and maximum voltage 872 V, is applied across a 51 W light bulb. When the voltage is first applied, what is the current through the circuit? 1. the rms current 2. correct 3. the maximum current Explanation: Let : t = 0 ....
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This note was uploaded on 11/02/2011 for the course PHYSICS 317L taught by Professor Erskine during the Fall '11 term at University of Texas at Austin.

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HW #8-solutions - nanni (arn437) HW #8 Erskine (56905) 1...

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