AC Fundamental- Electrical Engineering (MCQ) questions and answers
ELECTRICALGENIE
1. A sine wave has a frequency of 50 Hz. Its angular frequency is _______ radian/second.
2. The reactance offered by a capacitor to alternating current of frequency 50 Hz is 20 Q. If
frequency is increased to 100 Hz, reactance becomes_____ohms.
3. The period of a wave is
4. The form factor is the ratio of
5. The period of a sine wave is 20 milliseconds. Its frequency is
6. A heater is rated as 230 V, 10 kW, A.C. The value 230 V refers to
7. If two sinusoids of the same frequency but of different amplitudes and phase angles are subtracted,
the resultant is
8. The peak value of a sine wave is 200 V. Its average value is
9. If two sine waves of the same frequency have a phase difference of JT radians, then
10. The voltage of domestic supply is 220V. This figure represents
11. Two waves of the same frequency have opposite phase when the phase angle between them is
12. The power consumed in a circuit element will be least when the phase difference between the current and voltage is
13. The r.m.s. value and mean value is the same in the case of
14. For the same peak value which of the following wave will ‘have the highest r.m.s. value ?
15. For the same peak value, which of the following wave has the least mean value ?
16. For a sine wave with peak value Imax the r.m.s. value is
17. Form Factor is the ratio of
18. Form factor for a sine wave is
19. For a sine wave with peak value Emax______8.30. the average value is
20. For a frequency of 200 Hz, the time period will be
21. The phase difference between voltage and current wave through a circuit element is given as 30°.
The essential condition is that
22. The r.m.s. value of a sinusoidal A.C. current is equal to its value at an angle of______degrees.
23. Capacitive reactance is more when
24. In a series resonant circuit, the impedance of the circuit is
25. Power factor of an electrical circuit is equal to
26. Poor power factor
27. The best place to install a capacitor is
28. Capacitors for power factor correction are rated in
29. In series resonant circuit, increasing inductance to its twice value and reducing capacitance to its
half value
30. Pure inductive circuit
31. Inductance affects the direct current flow
32. Inductance of a coil Varies
33. All the rules and laws of D.C. circuit also apply to A.C. circuit containing
34. Time constant of an inductive circuit
35. In a highly capacitive circuit the
36. Power factor of the following circuit will be zero
37. Power factor of an inductive circuit is usually improved by connecting capacitor to it in
38. Power factor of the system is kept high
39. Power factor of the following circuit will be unity
40. The time constant of the capacitance circuit is defined as the time during which voltage
41. In a loss-free R-L-C circuit the transient current is
42. The r.m.s. value of alternating current is given by steady (D.C.) current which when flowing
through a given circuit for a given time produces
43. The square waveform of current has following relation between r.m.s. value and average value.
44. The double energy transient occur in the
45. The transient currents are associated with the
46. The power factor at resonance in R-L- C parallel circuit is
47. In the case of an unsymmetrical alternating current the average value must always be taken over
48. In a pure resistive circuit
49. In a pure inductive circuit
50. In a circuit containing R, L and C, power loss can take place in
51. Inductance of coil
52. In any A.C. circuit always
53. Which of the following circuit component opposes the change in the circuit voltage ?
54. In a purely inductive circuit
55. Power factor of electric bulb is
56. Pure inductive circuit takes power from the A.C. line when
57. Time constant of a circuit is the time in seconds taken after the application of voltage to each
58. Time constant of an inductive circuit
59. Time constant of a capacitive circuit
60. Magnitude of current at resonance in R-L-C circuit
61.In a R-L-C circuit
62.In R-L-C series resonant circuit magnitude of resonance frequency can be changed by changing the value of
63.In a series R-L-C circuit at the resonant frequency the
64. The time constant of a series R-C circuit is given by
65.If resistance is 20 Q. and inductance is 27 in a R-L series circuit, then time constant of this circuit will be
66. Which of the following coil will have large resonant frequency ?
67. If a sinusoidal wave has frequency of 50 Hz with 30 A r.m.s. current which of the following equation represents this wave ?
68. The safest value of current the human body can carry for more than 3 second is
69. A pure inductance connected across 250 V, 50 Hz supply consumes 100 W.This consumption can be attributed to
70.The input of an A.C. circuit having power factor of 0.8 lagging is 40 kVA .The power drawn by the circuit is
71.The effective resistance of an iron-cored choke working on ordinary supply frequency is more than its true resistance because of
72. In an AC. circuit, a low value of kVAR compared with kW indicates
73. In AC. circuits, laminated iron is invariably used in order to
74. The ratio of active power to apparent power is known as factor.
75.All definitions of power factor of a series R-L-C circuit are correct except
76.The apparent power drawn by an A.C. circuit is 10 kVA and active power is 8 kW. The reactive power in the circuit is
77. What will be the phase angle between two alternating waves of equal frequency, when one wave attains maximum value the other is at zero value ?
78. The purpose of a parallel circuit resonance is to magnify
79. In an A.C. circuit power is dissipated in
80.In a parallel R-C circuit, the current always______the applied voltage
81.At very low frequencies a series R-C circuit behaves as almost purely
82. Skin effect occurs when a conductor carries current at_____ frequencies.
83. At ______ frequencies the parallel R-L circuit behaves as purely resistive.
84. In a sine wave the slope is constant
85.The power is measured in terms of decibles in case of
86. Capacitive susceptance is a measure of
87. Which of the following statements pertains to resistors only ?
88. Which of the following refers to a parallel circuit ?
89. A phasor is
90.A parallel AC. circuit in resonance will
91.Wire-wound resistors are unsuitable for use at high frequencies because they
92.The inductance of a coil can be increased by
93. In a three-phase supply floating neutral is undesirable because it way give rise to
94.Which of the following waves has the highest value of peak factor ?
95.The r.m.s. value of half wave rectified sine wave is 200 V. The r.m.s. value of full wave rectified AC. will be
96. The r.m.s. value of pure cosine function is
97. Ohm is unit of all of the following except
98. The series and parallel resonance on L-C circuit’ differs in that
99.The frequency of an alternating current is
100.A pure capacitor connected across an A.C. voltage consumed 50 W. This is due to
101.The power factor of a D.C. circuit is always
102. The product of apparent power and cosine of the phase angle between circuit voltage and current is
103. The equation of 50 Hz current sine wave having r.m.s. value of 60 A is
104. An A.C. voltage is impressed across a pure resistance of 3.5 ohms in parallel with a pure inductance of impedance of 3.5 ohms,
105.In a pure inductive circuit if the supply frequency is reduced to 1/2, the current will
106. In a pure capacitive circuit if the supply frequency is reduced to 1/2, the current will
107.When an alternating current passes through an ohmic resistance the electrical power converted into heat is
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