100+ Alternating Voltage and current and Resonance in AC Circuits Questions

                     

1. If the resonant frequency in a series RLC circuit is 50kHz along with a bandwidth of 1kHz, find the quality factor.
a) 5
b) 50
c) 100
d) 500
Answer: b

2. What is the SI unit for quality factor?
a) Hz
b) kHz
c) MHz
d) No unit
Answer: d

3. What happens to the quality factor when the bandwidth increases?
a) Increases
b) Decreases
c) Remains the same
d) Becomes zero
Answer: b

4. What happens to the quality factor when resonant frequency increases?
a) Increases
b) Decreases
c) Remains the same
d) Becomes zero
Answer: a

5. Resonance frequency occurs when __________________
a) XL=XC
b) XL>XC
c) XL<XC
d) Cannot be determined
Answer: a

6. The current leads the supply voltage in a series RLC circuit has its frequency _________ the resonant frequency.
a) Above
b) Below
c) Equal to
d) Cannot be determined
Answer: b
These are 100+ Alternating Voltage and current Resonance in AC Circuits Questions

7. What is the power factor of a series RLC circuit under resonance condition?
a) 0
b) 1
c) Infinity
d) 100
Answer: b

8. The current lags the supply voltage in a series RLC circuit has its frequency _________ the resonant frequency.
a) Above
b) Below
c) Equal to
d) Cannot be determined
Answer: a

9. What is the correct formula for quality factor?
a) Q=BW*fr
b) Q=BW/fr
c) Q=fr/BW
d) Q=fr2
Answer: c

11. Quality factor is also known as _________
a) Voltage magnification
b) Current magnification
c) Resistance magnification
d) Impedance magnification
Answer: a

12. At resonance condition, the voltage across the capacitor and inductor is _________ the source voltage.
a) Greater than
b) Less than
c) Equal to
d) Much less than
Answer: a

13. What is the voltage across the capacitor when the source voltage is 100V and the Q factor is 10?
a) 100V
b) 10V
c) 1000V
d) 0V
Answer: c

14. Find the Q factor when the voltage across the capacitor is 1000V and the source voltage is 100V.
a) 10
b) 20
c) 30
d) 40
Answer: a

15. Find the source voltage when the voltage across the capacitor is 1000V and the Q factor is 10.
a) 10V
b) 200V
c) 100V
d) 90V
Answer: c

16. What is the voltage across the inductor when the source voltage is 200V and the Q factor is 10?
a) 100V
b) 20V
c) 2000V
d) 0V
Answer: c

17. Find the Q factor when the voltage across the inductor is 2000V and the source voltage is 100V.
a) 10
b) 20
c) 30
d) 40
Answer: b
These are 100+ Alternating Voltage and current Resonance in AC Circuits Questions

18. Find the source voltage when the voltage across the inductor is 2000V and the Q factor is 20.
a) 10V
b) 200V
c) 100V
d) 90V
Answer: c

19. What happens to the voltage across the capacitor when the Q factor increases?
a) Increases
b) Decreases
c) Remains the same
d) Becomes zero
Answer: a

20. What happens to the voltage across the inductor when the Q factor decreases?
a) Increases
b) Decreases
c) Remains the same
d) Becomes zero
Answer: b

21. The energy stored in the capacitor is of _________ nature.
a) Electrostatic
b) Magnetic
c) Neither electrostatic nor magnetic
d) Either electrostatic or magnetic
Answer: a

22. The energy stored in the inductor is of _________ nature.
a) Electrostatic
b) Magnetic
c) Neither electrostatic nor magnetic
d) Either electrostatic or magnetic
Answer: b

23. At resonance, the circuit appears __________
a) Inductive
b) Capacitive
c) Either inductive or capacitive
d) Resistive
Answer: d

24. At resonance, the capacitive energy is ___________ inductive energy.
a) Greater than
b) Less than
c) Equal to
d) Depends on the circuit
Answer: c

25. At resonance, electrostatic energy is ___________ the magnetic energy.
a) Greater than
b) Less than
c) Equal to
d) Depends on the circuit
Answer: c
These are 100+ Alternating Voltage and current Resonance in AC Circuits Questions

26. The maximum magnetic energy stored in an inductor at any instance is?
a) E=LIm2/2
b) E=LIm/2
c) E=LIm2
d) E=LIm2*2
Answer: a

27. The maximum electrostatic energy stored in a capacitor at any instance is?
a) CVm2
b) 1/2*CVm2
c) CVm
d) CVm/2
Answer: b

28. Q is the ratio of?
a) Active power to reactive power
b) Reactive power to active power
c) Reactive power to average power
d) Reactive power to capacitive power
Answer: c

29. Find the value of Q if the reactive power is 10W and the average power is 5W.
a) 10
b) 5
c) 2
d) 1
Answer: c

30. Find the reactive power when the average power is 5W and Q=2.
a) 10W
b) 5W
c) 2W
d) 1W
Answer: a

31. The SI unit for bandwidth is?
a) Hz
b) Watt
c) kHz
d) kW
Answer: a

32. At bandwidth frequency range, the value of the current I is?
a) I=Im/2
b) I=Im2
c) I=Im
d) I=Im/√2
Answer: d

33. At bandwidth frequency range, the value of the voltage V is?
a) V=Vm/2
b) V=Vm2
c) V=Vm
d) V=Vm/√2
Answer: d

34. At resonance, bandwidth includes the frequency range that allows _____ percent of the maximum current to flow.
a) 33.33
b) 66.67
c) 50
d) 70.7
Answer: d

35. At resonance, bandwidth includes the frequency range that allows _____ percent of the maximum voltage to flow.
a) 33.33
b) 66.67
c) 50
d) 70.7
Answer: d

36. Find the value of current in the bandwidth range when the maximum value of current is 50A.
a) 56.65A
b) 35.36A
c) 45.34A
d) 78.76A
Answer: b

37. Find the value of voltage in the bandwidth range when the maximum value of voltage is 100 V.
a) 56.65 V
b) 35.36 V
c) 45.34 V
d) 70.72 V
Answer: d

38. Bandwidth is the difference of_____________________ frequencies.
a) half power
b) full power
c) double power
d) wattless
Answer: a

39. For a sharp resonance, bandwidth is ______________
a) low
b) high
c) zero
d) infinity
Answer: a

40. Current is maximum at __________ frequency of bandwidth.
a) left end
b) middle
c) right end
d) all end
Answer: b

41. Shape of the resonance curve depends upon the?
a) Q-factor
b) Voltage
c) Current
d) Either voltage or current
Answer: a
These are 100+ Alternating Voltage and current Resonance in AC Circuits Questions

42. A circuit is said to be selective if it has a _____ peak and ____ bandwidth.
a) Blunt, narrow
b) Sharp, narrow
c) Sharp, broad
d) Blunt, broad
Answer: b

43. What is the Q factor of a selective circuit?
a) Very low
b) Very high
c) Zero
d) Infinity
Answer: b

44. In selective circuits, higher the Q factor _________ the peak.
a) Sharper
b) Blunter
c) Neither sharper nor blunter
d) Either sharper or blunter
Answer: a

45. Q is a measure of _________
a) Resonance
b) Bandwidth
c) Selectivity
d) Either resonance or bandwidth
Answer: c

46. In selective circuits, the resonant frequency lies in the ________ of the bandwidth frequency range.
a) Beginning
b) End
c) Midpoint
d) Cannot be determined
Answer: c

47. In order for high selectivity, the resistance must be?
a) Small
b) Large
c) Negative
d) Positive
Answer: a

48. In a series RLC circuit, the phase difference between the voltage across the capacitor and the voltage across the resistor is?
a) 00
b) 900
c) 1800
d) 3600
Answer: b

49. In a series RLC circuit, the phase difference between the voltage across the inductor and the voltage across the resistor is?
a) 00
b) 900
c) 1800
d) 3600
Answer: b

50. In a series RLC circuit, the phase difference between the voltage across the capacitor and the voltage across the inductor is?
a) 00
b) 900
c) 1800
d) 3600
Answer: c

51. In a series RLC circuit, the phase difference between the voltage across the resistor and the current in the circuit is?
a) 00
b) 900
c) 1800
d) 3600
Answer: a
These are 100+ Alternating Voltage and current Resonance in AC Circuits Questions

52. In a series RLC circuit, the phase difference between the voltage across the capacitor and the current in the circuit is?
a) 00
b) 900
c) 1800
d) 3600
Answer: b

53. In a series RLC circuit, the phase difference between the voltage across the inductor and the current in the circuit is?
a) 00
b) 900
c) 1800
d) 3600
Answer: b

54. The current in the inductor lags the voltage in a series RLC circuit ___________ resonant frequency.
a) Above
b) Below
c) Equal to
d) Depends on the circuit
Answer: a

55. The current in the capacitor leads the voltage in a series RLC circuit ___________ resonant frequency.
a) Above
b) Below
c) Equal to
d) Depends on the circuit
Answer: b
These are 100+ Alternating Voltage and current Resonance in AC Circuits Questions

56. The current in the inductor ___________ the voltage in a series RLC circuit above the resonant frequency.
a) Leads
b) Lags
c) Equal to
d) Depends on the circuit
Answer: b

57. The current in the capacitor ___________ the voltage in a series RLC circuit below the resonant frequency.
a) Leads
b) Lags
c) Equal to
d) Depends on the circuit
Answer: a

58. In a series RLC circuit, the phase difference between the current in the capacitor and the current in the resistor is?
a) 00
b) 900
c) 1800
d) 3600
Answer: a

59. In a series RLC circuit, the phase difference between the current in the inductor and the current in the resistor is?
a) 00
b) 900
c) 1800
d) 3600
Answer: a

60. In a series RLC circuit, the phase difference between the current in the capacitor and the current in the inductor is?
a) 00
b) 900
c) 1800
d) 3600
Answer: a

61. In a series RLC circuit, the phase difference between the current in the circuit and the voltage across the resistor is?
a) 00
b) 900
c) 1800
d) 3600
Answer: a

62. In a series RLC circuit, the phase difference between the current in the circuit and the voltage across the capacitor is?
a) 00
b) 900
c) 1800
d) 3600
Answer: b

63. _________ the resonant frequency, the current in the inductor lags the voltage in a series RLC circuit.
a) Above
b) Below
c) Equal to
d) Depends on the circuit
Answer: a

64. _________ the resonant frequency, the current in the capacitor leads the voltage in a series RLC circuit.
a) Above
b) Below
c) Equal to
d) Depends on the circuit
Answer: b

65. Which, among the following, is the correct expression for alternating emf generated?
a) e=2Blvsin(θ)
b) e=2B2lvsin(θ)
c) e=Blvsin(θ)
d) e=4Blvsin(θ)
Answer: c

66. What should theta be in order to get maximum emf?
a) 00
b) 900
c) 1800
d) 450
Answer: b

67. Calculate the maximum emf when the velocity is 10m/s, the length is 3m and the magnetic field density is 5T.
a) 150V
b) 100V
c) 300V
d) 0V
Answer: a

68. When a coil is rotated in a magnetic field, the emf induced in it?
a) Is maximum
b) Is minimum
c) Continuously varies
d) Remains constant
Answer: c

69. emf is zero if the angle between velocity and length is _____
a) 00
b) 900
c) 2700
d) 450
Answer: a

70. In an A.C. generator, increase in number of turns in the coil _________
a) Increases emf
b) Decreases emf
c) Makes the emf zero
d) Maintains the emf at a constant value
Answer: a
These are 100+ Alternating Voltage and current Resonance in AC Circuits Questions

71. The number of cycles that occur in one second is termed as ___________
a) Waveform
b) Frequency
c) Amplitude
d) Period
Answer: b

72. The variation of a quantity such as voltage or current shown on a graph is known as ___________
a) Waveform
b) Peak value
c) Instantaneous value
d) Period
Answer: a

73. What is the duration of one cycle known as _________
a) Waveform
b) Peak value
c) Instantaneous value
d) Period
Answer: d

74. The repetition of a variable quantity, recurring at equal intervals, is known as ___________
a) Waveform
b) Instantaneous value
c) Cycle
d) Period
Answer: c

75. The value of a given waveform at any instant time is termed as ___________
a) Waveform
b) Instantaneous value
c) Cycle
d) Period
Answer: b

76. The maximum instantaneous value measured from zero value is known as?
a) Peak value
b) Peak to peak value
c) Cycle
d) Period
Answer: a

77. The maximum variation between the maximum positive and the maximum negative value is known as?
a) Peak value
b) Peak to peak value
c) Cycle
d) Period
Answer: b

78. What is the correct relation between the peak value and peak to peak value for a sinusoidal waveform?
a) Vp=4Vp-p
b) Vp=Vp-p
c) Vp-p=2Vp
d) Vp=2Vp-p
Answer: c
These are 100+ Alternating Voltage and current Resonance in AC Circuits Questions

79. If the peak to peak voltage is 10V, calculate the peak voltage.
a) 10V
b) 2V
c) 4V
d) 5V
Answer: d

80. If the peak voltage is 9V, calculate the peak to peak voltage.
a) 9V
b) 20V
c) 18V
d) 12V
Answer: c

81. The waveform of the emf generated undergoes one complete cycle when?
a) Conductors move past north pole
b) Conductors move past south pole
c) Conductors move past north and south poles
d) Conductors are stationary
Answer: c

82. When is the shape of the negative half of the emf waveform equal to the positive half?
a) When the conductors move past north pole
b) When conductors move past south pole
c) When conductors move past both north and south pole
d) When conductors are stationary
Answer: c

83. Which is the correct formula for frequency in an ac generator?
a) f=p*n
b) f=p/n
c) f=n/p
d) f=n2p
Answer: a

84. What will happen to the frequency if the number of revolutions increases?
a) Increases
b) Decreases
c) Remains the same
d) Becomes zero
Answer: a

85. What happens to the frequency if the number of pairs of poles increases?
a) Increases
b) Decreases
c) Remains the same
d) Becomes zero
Answer: a

86. Calculate the frequency if the number of revolutions is 300 and the paired poles are 50.
a) 15kHz
b) 150kHz
c) 1500kHz
d) 150Hz
Answer: a

87. Calculate the number of revolutions if the frequency is 15kHz and the paired poles are 50.
a) 100
b) 200
c) 300
d) 400
Answer: c

These are 100+ Alternating Voltage and current Resonance in AC Circuits Questions


88. Calculate the number of paired poles if the frequency id 15kHz and the number of revolutions is 300.
a) 10
b) 30
c) 50
d) 70
Answer: c

89. What is the frequency of a two pole machine having n=50?
a) 100Hz
b) 200Hz
c) 50Hz
d) 25Hz
Answer: c

90. What is the minimum number of poles that a machine must have __________
a) 1
b) 2
c) 4
d) 10
Answer: b

91. Find the average value of current when the current that are equidistant are 4A, 5A and 6A.
a) 5A
b) 6A
c) 15A
d) 10A
Answer: a

92. What is the current found by finding the current in an equidistant region and dividing by n?
a) RMS current
b) Average current
c) Instantaneous current
d) Total current
Answer: b

93. RMS stands for ________
a) Root Mean Square
b) Root Mean Sum
c) Root Maximum sum
d) Root Minimum Sum
Answer: a

94. What is the type of current obtained by finding the square of the currents and then finding their average and then fining the square root?
a) RMS current
b) Average current
c) Instantaneous current
d) Total current
Answer: a

95. __________ current is found by dividing the area enclosed by the half cycle by the length of the base of the half cycle.
a) RMS current
b) Average current
c) Instantaneous current
d) Total current
Answer: b

96. What is the effective value of current?
a) RMS current
b) Average current
c) Instantaneous current
d) Total current
Answer: a

97. In a sinusoidal wave, average current is always _______ rms current.
a) Greater than
b) Less than
c) Equal to
d) Not related
Answer: b

98. For a rectangular wave, average current is ______ rms current.
a) Greater than
b) Less than
c) Equal to
d) Not related
Answer: c

99. Peak value divided by the rms value gives us?
a) Peak factor
b) Crest factor
c) Both peak and crest factor
d) Neither peak nor crest factor
Answer: c

100. Calculate the crest factor if the peak value of current is 10A and the rms value is 2A.
a) 5
b) 10
c) 5A
d) 10A
Answer: a
These are 100+ Alternating Voltage and current Resonance in AC Circuits Questions

101. If maximum value of current is 5√2 A, what will be the value of RMS current?
a) 10 A
b) 5 A
c) 15 A
d) 25 A
Answer: b

102. If Im is the maximum value of a sinusoidal voltage, what is the instantaneous value?
a) i=Im/2
b) i=Imsinθ
c) i=Imcosθ
d) i=Imsinθ or i=Imcosθ
Answer: d

103. Average value of current over a half cycle is?
a) 0.67Im
b) 0.33Im
c) 6.7Im
d) 3.3Im
Answer: a

104. What is the correct expression for the rms value of current?
a) Irms=Im/2
b) Irms=Im/√2
c) Irms=Im/4
d) Irms=Im
Answer: b

105. Average value of current over a full cycle is?
a) 0.67Im
b) 0
c) 6.7Im
d) 3.3Im
Answer: b

106. What is the correct expression for the form factor?
a) Irms * Iav
b) Irms / Iav
c) Irms + Iav
d) Irms – Iav
Answer: b

107. For a direct current, the rms current is ________ the mean current.
a) Greater than
b) Less than
c) Equal to
d) Not related to
Answer: c

108. For a direct current, the rms voltage is ________ the mean voltage.
a) Greater than
b) Less than
c) Equal to
d) Not related to
Answer: c

109. What is the value of the form factor for sinusoidal current?
a) π/2
b) π/4
c) 2π
d) π/√2
Answer: a

110. If the maximum value of the current is 5√2 A, what will be the value of the average current?
a) 10/π A
b) 5/π A
c) 15/π A
d) 25/π A
Answer: a

111. For addition and subtraction of phasors, we use the _________ form.
a) Rectangular
b) Polar
c) Either rectangular or polar
d) Neither rectangular nor polar
Answer: a

112. For multiplication and division of phasors, we use ____________ form.
a) Rectangular
b) Polar
c) Either rectangular or polar
d) Neither rectangular nor polar
Answer: b

These are 100+ Alternating Voltage and current Resonance in AC Circuits Questions

113. If a voltage of 2+5j and another voltage of 3+ 6j flows through two different resistors, connected in series, in a circuit, find the total voltage in the circuit.
a) 2+5j V
b) 3+6j V
c) 5+11j V
d) 5+10j V
Answer: c

114. Find the total current in the circuit if two currents of 4+5j flow in the circuit.
a) 4+5j A
b) 4A
c) 5A
d) 8+10j A
Answer: d

115. What is the correct expression of ω?
a) ω=2π
b) ω=2πf
c) ω=πf
d) ω=2f2
Answer: b

116. Find the value of ω if the frequency is 5Hz?
a) 3.14 rad/s
b) 31.4 rad/s
c) 34 rad/s
d) 341 rad/s
Answer: b

117. When one sine wave passes through the zero following the other, it is _________
a) Leading
b) Lagging
c) Neither leading nor lagging
d) Either leading or lagging
Answer: b

118. A phasor has frozen at 30 degrees, find the value of the phase angle.
a) 30 degrees
b) 60 degrees
c) 120 degrees
d) 180 degrees
Answer: a

119. The time axis of an AC phasor represents?
a) Time
b) Phase angle
c) Voltage
d) Current
Answer: b

120. The length of the phasor represents?
a) Magnitude of the quantity
b) Direction of the quantity
c) Neither magnitude nor direction
d) Either magnitude or direction
Answer: a

121. Ammeters and voltmeters are calibrated to read?
a) RMS value
b) Peak value
c) Average value
d) Instantaneous value
Answer: a

122. The rms value is _________ times he maximum value
a) 1.414
b) 0.5
c) 2
d) 0.707
Answer: d

123. The rms value is 0.707 times the _________ value.
a) Peak
b) Instantaneous
c) Average
d) DC
Answer: a

124. If the phasors are drawn to represent the maximum values instead of the rms values, what would happen to the phase angle between quantities?
a) Increases
b) Decreases
c) Remains constant
d) Becomes zero
Answer: c

125. Usually phasor diagrams are drawn representing?
a) RMS value
b) Peak value
c) Average value
d) Instantaneous value
Answer: a

126. If two current phasors, having magnitude 12A and 5A intersect at an angle of 90 degrees, calculate the resultant current.
a) 13 A
b) 10 A
c) 6 A
d) 5 A
Answer: a

127. If two current phasors, having magnitude 5A and 10A intersect at an angle of 60 degrees, calculate the resultant current.
a) 12.23 A
b) 12.54 A
c) 13.23 A
d) 14.24 A
Answer: c

128. The instantaneous values of two alternating voltages are given as _________
v1=60sinθ and v2=40sin(θ − π/3). Find the instantaneous sum.
a) 87.2 sin(36.5°) V
b) 87.2 sin( 0.5°) V
c) 87.2 sin(26.5°) V
d) 87.2 cos(36.5°) V
Answer: a

129. The instantaneous values of two alternating voltages are given as:
v1=60sinθ and v2=40sin(θ − π/3). Find the instantaneous difference.
a) 53 sin(71.5°) V
b) 53 sin( 79..5°) V
c) 53 sin(26.5°) V
d) 53 cos(36.5°) V
Answer: b

130. The resultant of two alternating sinusoidal voltages or currents can be found using ___________
a) Triangular law
b) Parallelogram law
c) Either triangular or parallelogram law
d) Neither triangular nor parallelogram law
Answer: b

These are 100+ Alternating Voltage and current Resonance in AC Circuits Questions


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