# Chap 31

B
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
C
. 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
We will write a custom essay sample on
Chap 31
or any similar topic only for you
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
B
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
C
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
B
. 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
D
Which of the following has the greatest effect in decreasing the oscillation frequency of an LC
A. L/2 and C/2
B. L/2 and 2C
C. 2L and C/2
D. 2L and 2C
E. none of these
C
We desire to make an LC circuit that oscillates at 100 Hz using an inductance of 2.5 H. We
also need a capacitance of:
A. 1 F
B. 1 mF
C. 1 µF
D. 100 µF
E. 1 pF
D
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
C
10. An LC circuit has an oscillation frequency of 105 Hz. If C = 0.1 µF, then L must be about:
A. 10 mH
B. 1 mH
C. 25 µH
D. 2.5 µH
E. 1 pH
B
Radio receivers are usually tuned by adjusting the capacitor of an LC circuit. If C = C1 for a
frequency of 600 kHz, then for a frequency of 1200 kHz one must adjust C to:
A. C1/2
B. C1/4
C. 2C1
D. 4C1
E. √2C1
C
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
D
The electrical analog of a spring constant k is:
A. L
B. 1/L
C. C
D. 1/C
E. R
C
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
A
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. 2.3 A
E. 5.3 A
B
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
C
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
C
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
E
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
C
The total energy in an LC circuit is 5.0 × 10−6 J. If C = 15 µF the charge on the capacitor is:
A. 0.82 µC
B. 8.5 µC
C. 12 µC
D. 17 µC
E. 24 µC
C
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
D
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. 6.7 mA
D. 15 mA
E. 15 A
C
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
D
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
E
An LC circuit has an inductance of 15 mH and a capacitance of 10 µF. At one instant the
charge on the capacitor is 25 µC. At that instant the current is changing at the rate of:
A. 0
B. 1.7 × 10−8 A/s
C. 5.9 × 10−3 A/s
D. 3.8 × 10−2 A/s
E. 170 A/s
C
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 current is:
A. 18 mA
B. 20 mA
C. 25 mA
D. 35 mA
E. 42 mA
A
The graphs show the total electromagnetic energy in two RLC circuits as functions of time.
Which of the following statements might be true?
A. Circuit 1 has a smaller resistance and a larger inductance
B. Circuit 1 has a larger resistance and a smaller inductance
C. Circuit 1 has the same resistance and a larger inductance
D. Circuit 1 has a larger resistance and a larger capacitance
E. Circuit 1 has the same resistance and a smaller capacitance
C
An RLC circuit has a resistance of 200 Ω and an inductance of 15 mH. Its oscillation frequency
is 7000 Hz. At time t = 0 the current is 25 mA and there is no charge on the capacitor. After
five complete cycles the current is:
A. zero
B. 1.8 × 10−6 A
C. 2.1 × 10−4 A
D. 2.3 × 10−3 A
E. 2.5 × 10−2 A
A
An RLC circuit has an inductance of 25 mH and a capacitance of 5.0 µF. The charge on the
capacitor does NOT oscillate but rather decays exponentially to zero. The resistance in the
circuit must be:
A. greater than or equal to 20, 000Ω
B. less than 20, 000Ω but greater than 10, 000Ω
C. less than 10, 000Ω but greater than 5, 000Ω
D. less than 5, 000Ω but greater than 0
E. 0
ans: A
A
A series circuit with an inductance of 15 mH, a capacitance of 35 µF, and a resistance of 5.0 Ω
contains a sinusoidal source of emf with a frequency of 500 Hz. The frequency with which the
charge on the capacitor oscillates is:
A. 500 Hz
B. 1.4 kHz
C. greater than 1.4 kHz
D. less than 500 Hz
E. between 500 Hz and 1.4 kHz
D
The rapid exponential decay in just a few cycles of the charge on the plates of capacitor in an
RLC circuit might be due to:
A. a large inductance
B. a large capacitance
C. a small capacitance
D. a large resistance
E. a small resistance
B
An RLC circuit has a capacitance of 12 µF, an inductance of 25 mH, and a resistance of 60Ω.
The current oscillates with an angular frequency of:
C
The angular frequency of a certain RLC series circuit is ω0. A source of sinusoidal emf, with
angular frequency 2ω, is inserted into the circuit. After transients die out the angular frequency
of the current oscillations is:
A. ω0/2
B. ω0
C. 2ω0
D. 1.5ω0
E. 3ω0
C
The angular frequency of a certain RLC series circuit is ω0. A source of sinusoidal emf, with
angular frequency ω, is inserted into the circuit and ω is varied while the amplitude of the
source is held constant. For which of the following values of ω is the amplitude of the current
oscillations the greatest?
A. ω0/5
B. ω0/2
C. ω0
D. 2ω0
E. None of them (they all produce the same current amplitude)
ans:
C
An RLC circuit has a sinusoidal source of emf. The average rate at which the source supplies
energy is 5 nW. This must also be:
A. the average rate at which energy is stored in the capacitor
B. the average rate at which energy is stored in the inductor
C. the average rate at which energy is dissipated in the resistor
D. twice the average rate at which energy is stored in the capacitor
E. three times the average rate at which energy is stored in the inductor
A
In a purely capacitive circuit the current:
A. leads the voltage by one-fourth of a cycle
B. leads the voltage by one-half of a cycle
C. lags the voltage by one-fourth of a cycle
D. lags the voltage by one-half of a cycle
E. is in phase with the potential difference across the plates
E
n a purely resistive circuit the current:
A. leads the voltage by one-fourth of a cycle
B. leads the voltage by one-half of a cycle
C. lags the voltage by one-fourth of a cycle
D. lags the voltage by one-half of a cycle
E. is in phase with the voltage
B
n a purely inductive circuit, the current lags the voltage by:
A. zero
B. one-fourth of a cycle
C. one-half of a cycle
D. three-fourths of a cycle
E. one cycle
B
A series RL circuit is connected to an emf source of angular frequency ω. The current:
A. leads the applied emf by tan−1(ωL/R)
B. lags the applied emf by tan−1(ωL/R)
C. lags the applied emf by tan−1(ωR/L)
D. leads the applied emf by tan−1(ωR/L)
E. is zero
A
A series RC circuit is connected to an emf source having angular frequency ω. The current:
A. leads the source emf by tan−1(1/ωCR)
B. lags the source emf by tan−1(1/ωCR)
C. leads the source emf by tan−1(ωCR)
D. lags the source emf by tan−1(ωCR)
E. leads the source emf by π/4
C
In an RLC series circuit, which is connected to a source of emf Em cos(ωt), the current lags
the voltage by 45◦ if:
A. R = 1/ωC − ωL
B. R = 1/ωL − ωC
C. R = ωL − 1/ωC
D. R = ωC − 1/ωL
E. ωL = 1/ωC
D
The reactance in ohms of a 35-µF capacitor connected to a 400-Hz generator is:
A. 0
B. 0.014
C. 0.088
D. 11
E. 71
C
A coil has a resistance of 60 Ω and an impedance of 100 Ω. Its reactance, in ohms, is:
A. 40
B. 60
C. 80
D. 117
E. 160
C
A 35-µF capacitor is connected to a source of sinusoidal emf with a frequency of 400 Hz and a
maximum emf of 20 V. The maximum current is:
A. 0
B. 0.28 A
C. 1.8 A
D. 230 A
E. 1400 A
D
The impedance of an RLC series circuit is definitely increased if:
A. C decreases
B. L increases
C. L decreases
D. R increases
E. R decreases
A
An RLC series circuit has R = 4 Ω, XC = 3 Ω, and XL = 6 Ω. The impedance of this circuit
is:
A. 5 Ω
B. 7 Ω
C. 9.8 Ω
D. 13 Ω
E. 7.8 Ω
E
The impedance of the circuit shown is:

50 Hz, 240 Vrms

A. 21 Ω
B. 50 Ω
C. 63 Ω
D. 65 Ω
E. 98 Ω

B
An electric motor, under load, has an effective resistance of 30 Ω and an inductive reactance of
40 Ω. When powered by a source with a maximum voltage of 420 V, the maximum current is:
A. 6.0 A
B. 8.4 A
C. 10.5 A
D. 12.0 A
E. 14.0 A
C
An RL series circuit is connected to an ac generator with a maximum emf of 20 V. If the
maximum potential difference across the resistor is 16 V, then the maximum potential difference
across the inductor is:
A. 2 V
B. 4 V
C. 12 V
D. 25.6 V
E. 36 V
E
When the amplitude of the oscillator in a series RLC circuit is doubled:
A. the impedance is doubled
B. the voltage across the capacitor is halved
C. the capacitive reactance is halved
D. the power factor is doubled
E. the current amplitude is doubled
B
When the frequency of the oscillator in a series RLC circuit is doubled:
A. the capacitive reactance is doubled
B. the capacitive reactance is halved
C. the impedance is doubled
D. the current amplitude is doubled
E. the current amplitude is halved
B
. In an RLC series circuit, the source voltage is leading the current at a given frequency f. If f
is lowered slightly, then the circuit impedance will:
A. increase
B. decrease
C. remain the same
D. need to know the amplitude of the source voltage
E. need to know whether the phase angle is larger or smaller than 45◦
ans: B
D
In the diagram, the function y(t) = ym sin(ωt) is plotted as a solid curve. The other three
curves have the form y(t) = ym sin(ωt + φ), where φ is between −π/2 and +π/2. Rank the
curves according to the value of φ, from the most negative to the most positive.
t
y(t)
A. 1, 2, 3
B. 2, 3, 1
C. 3, 2, 1
D. 1, 3, 2
E. 2, 1, 3
B
An RLC series circuit is driven by a sinusoidal emf with angular frequency ωd. If ωd is
increased without changing the amplitude of the emf the current amplitude increases. If L is
the inductance, C is the capacitance, and R is the resistance, this means that:
A. ωdL > 1/ωdC
B. ωdL < 1/ωdC C. ωdL = 1/ωdC D. ωdL>R
E. ωdL
B
An RLC series circuit has L = 100 mH and C = 1 µF. It is connected to a 1000-Hz source and
the source emf is found to lead the current by 75◦. The value of R is:
A. 12.6 Ω
B. 126 Ω
C. 175 Ω
D. 1750 Ω
E. 1810 Ω
E
In a sinusoidally driven series RLC circuit, the inductive reactance is XL = 200 Ω, the capacitive
reactance is XC = 100 Ω, and the resistance is R = 50 Ω. The current and applied emf
would be in phase if:
A. the resistance is increased to 100 Ω, with no other changes
B. the resistance is increased to 200 Ω, with no other changes
C. the inductance is reduced to zero, with no other changes
D. the capacitance is doubled, with no other changes
E. the capacitance is halved, with no other changes`
A
In a sinusoidally driven series RLC circuit the current lags the applied emf. The rate at which
energy is dissipated in the resistor can be increased by:
A. decreasing the capacitance and making no other changes
B. increasing the capacitance and making no other changes
C. increasing the inductance and making no other changes
D. increasing the driving frequency and making no other changes
E. decreasing the amplitude of the driving emf and making no other changes
B
An RLC series circuit, connected to a source E, is at resonance. Then:
A. the voltage across R is zero
B. the voltage across R equals the applied voltage
C. the voltage across C is zero
D. the voltage across L equals the applied voltage
E. the applied voltage and current differ in phase by 90
E
An RLC series circuit is connected to an oscillator with a maximum emf of 100 V. If the
voltage amplitudes VR, VL, and VC are all equal to each other, then VR must be:
A. 33 V
B. 50 V
C. 67 V
D. 87 V
E. 100 V
B
A resistor, an inductor, and a capacitor are connected in parallel to a sinusoidal source of emf.
Which of the following is true?
A. The currents in all branches are in phase.
B. The potential differences across all branches are in phase.
C. The current in the capacitor branch leads the current in the inductor branch by one-fourth
of a cycle
D. The potential difference across the capacitor branch leads the potential difference across
the inductor branch by one-fourth of a cycle.
E. The current in the capacitor branch lags the current in the inductor branch by one-fourth
of a cycle.
C
The rms value of an ac current is:
A. its peak value
B. its average value
C. that steady current that produces the same rate of heating in a resistor as the actual
current
D. that steady current that will charge a battery at the same rate as the actual current
E. zero
D
The rms value of a sinusoidal voltage is V0/
√2, where V0 is the amplitude. What is the rms
value of its fully rectified wave? Recall that Vrect(t) = |V
A. V 20 /√2
B. V 20 /2
C. √2V0
D. V0/√2
E. V0/(2√2)
D
A sinusoidal voltage V (t) has an rms value of 100 V. Its maximum value is:
A. 100 V
B. 707 V
C. 70.7 V
D. 141 V
E. 200 V
D
An ac generator produces 10 V (rms) at 400 rad/s. It is connected to a series RL circuit
(R = 17.3 Ω, L = 0.025 H). The rms current is:
A. 0.50 A and leads the emf by 30◦
B. 0.71 A and lags the emf by 30◦
C. 1.40 A and lags the emf by 60◦
D. 0.50 A and lags the emf by 30◦
E. 0.58 A and leads the emf by 90◦
B
An ac generator producing 10 V (rms) at 200 rad/s is connected in series with a 50-Ω resistor,
a 400-mH inductor, and a 200-µF capacitor. The rms current in amperes is:
A. 0.125
B. 0.135
C. 0.18
D. 0.20
E. 0.40
ans: B
C
An ac generator producing 10 V (rms) at 200 rad/s is connected in series with a 50-Ω resistor,
a 400-mH inductor, and a 200-µF capacitor. The rms voltage (in volts) across the resistor is:
A. 2.5
B. 3.4
C. 6.7
D. 10.0
E. 10.8
B
An ac generator producing 10 V (rms) at 200 rad/s is connected in series with a 50-Ω resistor,
a 400-mH inductor, and a 200-µF capacitor. The rms voltage (in volts) across the capacitor is:
A. 2.5
B. 3.4
C. 6.7
D. 10.0
E. 10.8
E
An ac generator producing 10 V (rms) at 200 rad/s is connected in series with a 50-Ω resistor,
a 400-mH inductor, and a 200-µF capacitor. The rms voltage (in volts) across the inductor is:
A. 2.5
B. 3.4
C. 6.7
D. 10.0
E. 10.8
C
The ideal meters shown read rms current and voltage. The average power delivered to the load
is:

unknown
A. definitely equal to V I
B. definitely more than V I
C. possibly equal to V I even if the load contains an inductor and a capacitor
D. definitely less than V I
E. zero, as is the average of any sine wave

B
The average power supplied to the circuit shown passes through a maximum when which one
of the following is increased continuously from a very low to a very high value?
………………………………………………………………………………
E, f C
A. Source emf E
B. R
C. C
D. Source frequency f
E. None of these
E
In a series RLC circuit the rms value of the generator emf is E and the rms value of the current
is i. The current lags the emf by φ. The average power supplied by the generator is given by:
A. (iE/2) cos φ
B. iE
C. i
2/Z
D. i2Z
E. i2R
E
The units of the power factor are:
A. ohm
B. watt
D. ohm1/2
E. none of these
C
A series circuit consists of a 15-Ω resistor, a 25-mH inductor, and a 35-µF capacitor. If the
frequency is 100 Hz the power factor is:
A. 0
B. 0.20
C. 0.45
D. 0.89
E. 1.0
B
The main reason that alternating current replaced direct current for general use is:
A. ac generators do not need slip rings
B. ac voltages may be conveniently transformed
C. electric clocks do not work on dc
D. a given ac current does not heat a power line as much as the same dc current
E. ac minimizes magnetic effects
D
A step-down transformer is used to:
A. increase the power
B. decrease the power
C. increase the voltage
D. decrease the voltage
E. change ac to dc
C
Iron, rather than copper, is used in the core of transformers because iron:
A. can withstand a higher temperature
B. has a greater resistivity
C. has a very high permeability
D. makes a good permanent magnet
E. insulates the primary from the secondary
E
The core of a transformer is made in a laminated form to:
A. facilitate easy assembly
B. reduce i
2R losses in the coils
C. increase the magnetic flux
D. save weight
E. prevent eddy currents
A
A generator supplies 100 V to the primary coil of a transformer. The primary has 50 turns and
the secondary has 500 turns. The secondary voltage is:
A. 1000 V
B. 500 V
C. 250 V
D. 100 V
E. 10 V
A
The resistance of the primary coil of a well-designed, 1 : 10 step-down transformer is 1 Ω. With
the secondary circuit open, the primary is connected to a 12 V ac generator. The primary
current is:
A. essentially zero
D. depends on the actual number of turns in the primary coil
E. depends on the core material
D
The primary of an ideal transformer has 100 turns and the secondary has 600 turns. Then:
A. the power in the primary circuit is less than that in the secondary circuit
B. the currents in the two circuits are the same
C. the voltages in the two circuits are the same
D. the primary current is six times the secondary current
E. the frequency in the secondary circuit is six times that in the primary circui
A
The primary of a 3 : 1 step-up transformer is connected to a source and the secondary is
connected to a resistor R. The power dissipated by R in this situation is P. If R is connected
directly to the source it will dissipate a power of:
A. P/9
B. P/3
C. P
D. 3P
E. 9P
B
In an ideal 1 : 8 step-down transformer, the primary power is 10 kW and the secondary current
is 25 A. The primary voltage is:
A. 25, 600 V
B. 3200 V
C. 400 V
D. 50 V
E. 6.25 V
C
. A source with an impedance of 100 Ω is connected to the primary coil of a transformer and a
resistance R is connected to the secondary coil. If the transformer has 500 turns in its primary
coil and 100 turns in its secondary coil the greatest power will be dissipated in the resistor if
R =:
A. 0
B. 0.25 Ω
C. 4.0 Ω
D. 50 Ω
E. 100 Ω

#### New Essays

×

Hi there, would you like to get such a paper? How about receiving a customized one? Check it out