Halliday D., Resnick R., Walker J. Fundamentals of physics. Test Bank
Подождите немного. Документ загружается.
69. Immediately after switch S in the circuit shown is closed, the current through the battery is:
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S
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1
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A. 0
B. V
0
/R
1
C. V
0
/R
2
D. V
0
/(R
1
+ R
2
)
E. V
0
(R
1
+ R
2
)/(R
1
R
2
)
ans: D
70. A 3.5-mH inductor and a 4.5-mH inductor are connected in series. The equivalent inductance
is:
A. 2.0mH
B. 0.51 mH
C. 0.13 mH
D. 1.0mH
E. 8.0mH
ans: E
71. A 3.5-mH inductor and a 4.5-mH inductor are connected in series and a time varying current
is established in them. When the total emf of the combination is 16 V, the emf of the larger
inductor is:
A. 7.0V
B. 9.0V
C. 2.3V
D. 28 V
E. 36 V
ans: B
72. A 3.5-mH inductor and a 4.5-mH inductor are connected in parallel. The equivalent inductance
is:
A. 2.0mH
B. 0.51 mH
C. 0.13 mH
D. 1.0mH
E. 8.0mH
ans: A
Chapter 30: INDUCTION AND INDUCTANCE 451
73. A 3.5-mH inductor and a 4.5-mH inductor are connected in parallel. When the total emf of
the combination is 16 V, the rate of change of the current in the larger inductor is:
A. 2.0 × 10
3
A/s
B. 3.6 × 10
3
A/s
C. 4.6 × 10
3
A/s
D. 7.0 × 10
3
A/s
E. 8.1 × 10
3
A/s
ans: B
74. An inductor with inductance L and an inductor with inductance 2L are connected in parallel.
When the rate of change of the current in the larger inductor is 1200 A/s the rate of change of
the current in the smaller inductor is:
A. 400 A/s
B. 1200 A/s
C. 1600 A/s
D. 2000 A/s
E. 2400 A/s
ans: E
75. The stored energy in an inductor:
A. depends, in sign, upon the direction of the current
B. depends on the rate of change of current
C. is proportional to the square of the inductance
D. has units J/H
E. none of the above
ans: E
76. An inductance L and a resistance R are connected in series to an ideal battery. A switch in the
circuit is closed at time 0, at which time the current is zero. The energy stored in the inductor
is a maximum:
A. just after the switch is closed
B. at the time t = L/R after the switch is closed
C. at the time t = L/R after the switch is closed
D. at the time t =2L/R after the switch is closed
E. a long time after the switch is closed
ans: E
77. An inductance L and a resistance R are connected in series to an ideal battery. A switch in
the circuit is closed at time 0, at which time the current is zero. The rate of increase of the
energy stored in the inductor is a maximum:
A. just after the switch is closed
B. at the time t = L/R after the switch is closed
C. at the time t = L/R after the switch is closed
D. at the time t =(L/R) ln 2 after the switch is closed
E. a long time after the switch is closed
ans: D
452 Chapter 30: INDUCTION AND INDUCTANCE
78. In each of the following operations, energy is expended. The LEAST percentage of returnable
electrical energy will be yielded by:
A. charging a capacitor
B. charging a storage battery
C. sending current through a resistor
D. establishing a current through an inductor
E. moving a conducting rod through a magnetic field
ans: C
79. A current of 10 A in a certain inductor results in a stored energy of 40 J. When the current is
changed to 5 A in the opposite direction, the stored energy changes by:
A. 20 J
B. 30 J
C. 40 J
D. 50 J
E. 60 J
ans: B
80. A 6.0-mH inductor is in a series circuit with a resistor and an ideal battery. At the instant the
current in the circuit is 5.0 A the energy stored in the inductor is:
A. 0
B. 7.5 × 10
−2
J
C. 15 × 10
−2
J
D. 30 × 10
−2
J
E. unknown since the rate of change of the current is not given
ans: B
81. A 6.0-mH inductor is in a circuit. At the instant the current is 5.0 A and its rate of change is
200 A/s, the rate with which the energy stored in the inductor is increasing is:
A. 7.5 × 10
−2
W
B. 120 W
C. 240 W
D. 3.0W
E. 6.0W
ans: E
82. A 6.0-mH inductor and a 3.0-Ω resistor are wired in series to a 12-V ideal battery. A switch in
the circuit is closed at time 0, at which time the current is zero. 2.0 ms later the energy stored
in the inductor is:
A. 0
B. 2.5 × 10
−2
J
C. 1.9 × 10
−2
J
D. 3.8 × 10
−2
J
E. 9.6 × 10
−3
J
ans: C
Chapter 30: INDUCTION AND INDUCTANCE 453
83. The quantity B
2
/µ
0
has units of:
A. J
B. J/H
C. J/m
D. J/m
3
E. H/m
3
ans: D
84. A 0.20-cm radius cylinder, 3.0 cm long, is wrapped with wire to form an inductor. At the
instant the magnetic field in the interior is 5.0 mT the energy stored in the field is about:
A. 0
B. 3.8 × 10
−6
J
C. 7.5 × 10
−6
J
D. 7.5 × 10
−4
J
E. 9.9J
ans: B
85. In the diagram, assume that all the magnetic field lines generated by coil 1 pass through coil
2. Coil 1 has 100 turns and coil 2 has 400 turns. Then:
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A. the power supplied to coil 1 is equal to the power delivered by coil 2
B. the emf around coil 1 will be one-fourth the emf around coil 2
C. the current in coil 1 will be one-fourth the current in coil 2
D. the emfs will be the same in the two coils
E. none of the above
ans: E
454 Chapter 30: INDUCTION AND INDUCTANCE
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. T/2
D. T
E. 2T
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. T/4
C. T/2
D. T
E. 2T
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. T/4
C. T/2
D. T
E. 2T
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 field of the inductor is a maximum is:
A. T
B. T/4
C. T/2
D. T
E. 2T
ans: B
Chapter 31: ELECTROMAGNETIC OSCILLATIONS & ALTERNATING CURRENT 455
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 field of the capacitor is a maximum is:
A. T
B. T/4
C. T/2
D. T
E. 2T
ans: C
6. A capacitor in an LC oscillator has a maximum potential difference of 15 V and a maximum
energy of 360 µJ. At a certain instant the energy in the capacitor is 40 µJ. At that instant
what is the potential difference 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 effect in decreasing the oscillation frequency of an LC
circuit? Using instead:
A. L/2 and C/2
B. L/2 and 2C
C. 2L and C/2
D. 2L and 2C
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 µF
D. 100 µF
E. 1 pF
ans: C
9. An LC circuit consists of a 1-µF 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.IfC=0.1 µF, then L must be about:
A. 10 mH
B. 1 mH
C. 25 µH
D. 2.5 µH
E. 1 pH
ans: C
11. In the circuit shown, switch S is first pushed up to charge the capacitor. When S is then pushed
down, the current in the circuit will oscillate at a frequency of:
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50 mH
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•
5 µF
V
0
.................................................................................................................................................................................................................................................................................................................
•
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S
A. 318 Hz
B. 0.01 Hz
C. 12.500 Hz
D. 2000 Hz
E. depends on V
0
ans: A
12. Radio receivers are usually tuned by adjusting the capacitor of an LC circuit. If C = C
1
for a
frequency of 600 kHz, then for a frequency of 1200 kHz one must adjust C to:
A. C
1
/2
B. C
1
/4
C. 2C
1
D. 4C
1
E.
√
2C
1
ans: B
13. An LC series circuit with an inductance L and a capacitance C has an oscillation frequency f.
Two inductors, each with inductance L, and two capacitors, each with capacitance C, are all
wired in series and the circuit is completed. The oscillation frequency is:
A. f/4
B. f/2
C. f
D. 2f
E. 4f
ans: C
Chapter 31: ELECTROMAGNETIC OSCILLATIONS & ALTERNATING CURRENT 457
14. The electrical analog of a spring constant k is:
A. L
B. 1/L
C. C
D. 1/C
E. R
ans: D
15. Consider the mechanical system consisting of two springs and a block, as shown. Which one
of the five electrical circuits (A, B, C, D, E) is the analog of the mechanical system?
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k
1
k
2
••••
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\\
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E
ans: A
16. A 150-g block on the end of a spring with a spring constant of 35 N/m is pulled aside 25 cm
and released from rest. In the electrical analog the initial charge on the capacitor is:
A. 0.15 C
B. 6.67 C
C. 0.025 C
D. 40 C
E. 35 C
ans: C
458 Chapter 31: ELECTROMAGNETIC OSCILLATIONS & ALTERNATING CURRENT
17. A 150-g block on the end of a spring with a spring constant of 35 N/m is pulled aside 25 cm
and released from rest. In the electrical analog the maximum charge on the capacitor is 0.25 C.
The maximum current in the LC circuit is:
A. 0.38 A
B. 0.025 A
C. 40 A
D. 2.3A
E. 5.3A
ans: A
18. A capacitor in an LC oscillator has a maximum potential difference of 15 V and a maximum
energy of 360 µJ. At a certain instant the energy in the capacitor is 40 µJ. At that instant
what is the potential difference across the capacitor?
A. zero
B. 5 V
C. 10 V
D. 15 V
E. 20 V
ans: B
19. A capacitor in an LC oscillator has a maximum potential difference of 15 V and a maximum
energy of 360 µJ. At a certain instant the energy in the capacitor is 40 µJ. At that instant
what is the emf induced in the inductor?
A. zero
B. 5 V
C. 10 V
D. 15 V
E. 20 V
ans: C
20. In an oscillating LC circuit, the total stored energy is U . The maximum energy stored in the
capacitor during one cycle is:
A. U/2
B. U/
√
2
C. U
D. U/(2π)
E. U/π
ans: C
21. In an oscillating LC circuit, the total stored energy is U and the maximum charge on the
capacitor is Q. When the charge on the capacitor is Q/2, the energy stored in the inductor is:
A. U/2
B. U/4
C. (4/3)U
D. 3U/2
E. 3U/4
ans: E
Chapter 31: ELECTROMAGNETIC OSCILLATIONS & ALTERNATING CURRENT 459
22. The total energy in an LC circuit is 5.0 × 10
−6
J.IfC=15µF the charge on the capacitor is:
A. 0.82 µC
B. 8.5 µC
C. 12 µC
D. 17 µC
E. 24 µC
ans: C
23. The total energy in an LC circuit is 5.0 × 10
−6
J. If L = 25 mH the maximum current is:
A. 10 mA
B. 14 mA
C. 20 mA
D. 28 mA
E. 40 mA
ans: C
24. At time t = 0 the charge on the 50-µF capacitor in an LC circuit is 15 µC and there is no
current. If the inductance is 20 mH the maximum current is:
A. 15 nA
B. 15 µA
C. 6.7mA
D. 15 mA
E. 15 A
ans: D
25. An LC circuit has an inductance of 20 mH and a capacitance of 5.0 µF. At time t = 0 the
charge on the capacitor is 3.0 µC and the current is 7 .0 mA. The total energy is:
A. 4.1 × 10
−7
J
B. 4.9 × 10
−7
J
C. 9.0 × 10
−7
J
D. 1.4 × 10
−6
J
E. 2.8 × 10
−6
J
ans: D
26. An LC circuit has a capacitance of 30 µF and an inductance of 15 mH. At time t = 0 the charge
on the capacitor is 10 µC and the current is 20 mA. The maximum charge on the capacitor is:
A. 8.9 µC
B. 10 µC
C. 12 µC
D. 17 µC
E. 24 µC
ans: D
460 Chapter 31: ELECTROMAGNETIC OSCILLATIONS & ALTERNATING CURRENT