# ch31 - Chapter 31: ELECTROMAGNETIC OSCILLATIONS AND...

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Chapter 31: ELECTROMAGNETIC OSCILLATIONS AND ALTERNATING CURRENT 1. A charged capacitor and an inductor are connected in series. At time t = 0 the current is zero, but the capacitor is charged. If T is the period of the resulting oscillations, the next time after t = 0 that the current is a maximum is: A. T B. T/ 4 C. 2 D. T E. 2 T ans: B 2. A charged capacitor and an inductor are connected in series. At time t = 0 the current is zero, but the capacitor is charged. If T is the period of the resulting oscillations, the next time after t = 0 that the charge on the capacitor is a maximum is: A. T B. 4 C. 2 D. T E. 2 T ans: C 3. A charged capacitor and an inductor are connected in series. At time t = 0 the current is zero, but the capacitor is charged. If T is the period of the resulting oscillations, the next time after t = 0 that the voltage across the inductor is a maximum is: A. T B. 4 C. 2 D. T E. 2 T ans: C 4. A charged capacitor and an inductor are connected in series. At time t = 0 the current is zero, but the capacitor is charged. If T is the period of the resulting oscillations, the next time after t = 0 that the energy stored in the magnetic f eld of the inductor is a maximum is: A. T B. 4 C. 2 D. T E. 2 T ans: B Chapter 31: ELECTROMAGNETIC OSCILLATIONS & ALTERNATING CURRENT 455

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5. A charged capacitor and an inductor are connected in series. At time t = 0 the current is zero, but the capacitor is charged. If T is the period of the resulting oscillations, the next time after t = 0 that the energy stored in the electric f eld of the capacitor is a maximum is: A. T B. T/ 4 C. 2 D. T E. 2 T ans: C 6. A capacitor in an LC oscillator has a maximum potential di f erence of 15 V and a maximum energy of 360 μ J. At a certain instant the energy in the capacitor is 40 μ J. At that instant what is the potential di f erence across the capacitor? A. zero B. 5 V C. 10 V D. 15 V E. 20 V ans: B 7. Which of the following has the greatest e f ect in decreasing the oscillation frequency of an LC circuit? Using instead: A. L/ 2 and C/ 2 B. L/ 2 and 2 C C. 2 L and 2 D. 2 L and 2 C E. none of these ans: D 8. We desire to make an LC circuit that oscillates at 100 Hz using an inductance of 2 . 5H. We also need a capacitance of: A. 1 F B. 1 mF C. 1 μ F D. 100 μ F E. 1 pF ans: C 9. An LC circuit consists of a 1- μ F capacitor and a 4 mH inductor. Its oscillation frequency is approximately: A. 0 . 025 Hz B. 25 Hz C. 60 Hz D. 2500 Hz E. 15 , 800 Hz ans: D 456 Chapter 31: ELECTROMAGNETIC OSCILLATIONS & ALTERNATING CURRENT
10. An LC circuit has an oscillation frequency of 10 5 Hz .I fC=0 . 1 μ F, then L must be about: A. 10 mH B. 1 mH C. 25 μ H D. 2 . 5 μ H E. 1 pH ans: C 11. In the circuit shown, switch S is f rst pushed up to charge the capacitor. When S is then pushed down, the current in the circuit will oscillate at a frequency of: . . . . . . . . . . . . . . .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ........ . . . . . . . . . . . 50 mH . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ..................................................... ............................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 μ F V 0 ....................................................................................................

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## This note was uploaded on 04/14/2008 for the course PHYSICS 108 taught by Professor Halstead during the Spring '08 term at SUNY Buffalo.

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ch31 - Chapter 31: ELECTROMAGNETIC OSCILLATIONS AND...

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