# 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) X_{L}=X_{C}

b) X_{L}>X_{C}

c) X_{L}<X_{C}

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=LI_{m}^{2}/2

b) E=LI_{m}/2

c) E=LI_{m}^{2}

d) E=LI_{m}^{2}*2**Answer: a**

27. The maximum electrostatic energy stored in a capacitor at any instance is?

a) CV_{m}^{2}

b) 1/2*CV_{m}^{2}

c) CV_{m}

d) CV_{m}/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=Im^{2}

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=Vm^{2}

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) 0^{0}

b) 90^{0}

c) 180^{0}

d) 360^{0}**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) 0^{0}

b) 90^{0}

c) 180^{0}

d) 360^{0}**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) 0^{0}

b) 90^{0}

c) 180^{0}

d) 360^{0}**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) 0^{0}

b) 90^{0}

c) 180^{0}

d) 360^{0}**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) 0^{0}

b) 90^{0}

c) 180^{0}

d) 360^{0}**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) 0^{0}

b) 90^{0}

c) 180^{0}

d) 360^{0}**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) 0^{0}

b) 90^{0}

c) 180^{0}

d) 360^{0}**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) 0^{0}

b) 90^{0}

c) 180^{0}

d) 360^{0}**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) 0^{0}

b) 90^{0}

c) 180^{0}

d) 360^{0}**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) 0^{0}

b) 90^{0}

c) 180^{0}

d) 360^{0}**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) 0^{0}

b) 90^{0}

c) 180^{0}

d) 360^{0}**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=2B^{2}lvsin(θ)

c) e=Blvsin(θ)

d) e=4Blvsin(θ)**Answer: c**

66. What should theta be in order to get maximum emf?

a) 0^{0}

b) 90^{0}

c) 180^{0}

d) 45^{0}**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) 0^{0}

b) 90^{0}

c) 270^{0}

d) 45^{0}**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=n^{2}p**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) I_{rms} * I_{av}

b) I_{rms} / I_{av}

c) I_{rms} + I_{av}

d) I_{rms} – I_{av}**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=2f^{2}**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

More in this series: 50+ Simple Magnetic Circuits Questions