PART 2

Question 1

51. If emf in a circuit is given by e = 100 sin 628t, the maximum value of voltage and frequency are

A. 100 V, 50 Hz

B. 50√2 V, 50 Hz

C. 100 V, 100 Hz

D. 50√2 V, 100 Hz

Answer 1

C

Question 2

52. When the sole purpose of an alternating current is to produce heat, the selection of conductor is based on

A. average value of current

B. peak value of current

C. rms value of current

D. any of the above

Answer 2

C

Question 3

53. The form factor of dc supply voltage is always

A. infinite

B. zero

C. 0.5

D. unity

Answer 3

A

Question 4

54. The frequency of a sinusoidal signal shown in figure is

EE Question Banks figure no. 54
A. 500 Hz

B. 1 kHz

C. 25 kHz

D. 500 kHz

Answer 4

A

Question 5

55. The period of the voltage 2 cos 4500πt + 7 sin 7500πt is

A. 2.51 s

B. 2.51 ns

C. 2.51 ms

D. 2.51 μs

Answer 5

C

Question 6

56. The a.c. system is preferred to d.c. system because ______

A. a.c. voltages can easily be changed in magnitude

B. d.c. motors do not have fine speed control

C. high-voltage a.c. transmissions is less efficient

D. d.c. voltage cannot be used for domestic appliance

Answer 6

A

Question 7

57. In a.c. system, we generate sine wave form because ______

A. it can be easily drawn

B. it produces lest disturbance in electrical circuits

C. it is nature’s standard

D. other waves cannot be produced easily

Answer 7

B

Question 8

58. ______ will work only on d.c. supply.

A. Electric lamp

B. Refrigerator

C. Heater

D. Electroplating

Answer 8

D

Question 9

59. ______ will produce a.c. voltage.

A. Friction

B. Photoelectric effect

C. Thermal energy

D. Crystal

Answer 9

D

Question 10

62. A coil is rotating in the uniform field of an 8-pole generator. In one revolution of the coil, the number of cycles generated by the voltage is ______.

A. one

B. two

C. four

D. eight

Answer 10

C

Question 11

63. An alternating voltage is given by v = 20 sin 157t. The frequency of the alternating voltage is ______.

A. 50 Hz

B. 25 Hz

C. 100 Hz

D. 75 Hz

Answer 11

B

Question 12

64. An alternating current is given by i = 10 sin 314t. The time taken to generate two cycles of current is ______.

A. 0.02 second

B. 0.01 second

C. 0.04 second

D. 0.05 second

Answer 12

C

Question 13

65. An alternating voltage is given by v = 30 sin 314t. The time taken by the voltage to reach -30 V for the first time is ______.

A. 0.02 second

B. 0.1 second

C. 0.03 second

D. 0.015 second

Answer 13

D

Question 14

66. A sine wave has a maximum value of 20 V. Its value at 135° is _____.

A. 10 V

B. 14.14 V

C. 15 V

D. 5 V

Answer 14

B

Question 15

67. A sinusoidal current has a magnitude of 3 A at 120°. Its maximum value will be ______.

A. √3 A

B. √3/2 A

C. 2√3 A

D. 6 A

Answer 15

C

Question 16

68. An alternating current given by i = 10 sin 314t. Measuring time from t = 0, the time taken by the current to reach +10 A for the second time is ______.

A. 0.05 second

B. 0.1 second

C. 0.025 second

D. 0.02 second

Answer 16

C

Question 17

69. An a.c. generator having 10 poles and running at 600 r.p.m. will generate an alternating voltage of frequency _______

A. 25 Hz

B. 100 Hz

C. 50 Hz

D. 200 Hz

Answer 17

C

Question 18

70. We have assigned a frequency of 50 Hz to power system because it ______

A. can easily be obtained

B. gives best result when used for operating both lights and machinery

C. leads to easy calculation

D. none of the above

Answer 18

B

Question 19

71. An alternating voltage is given by v = 100 sin 314t volts. Its average value will be ______.

A. 70.7 V

B. 50 V

C. 63.7 V

D. 100 V

Answer 19

C

Question 20

72. An alternating current whose average value is 1 A will produce ____ 1 A d.c. under similar conditions.

A. less heat than

B. more heat than

C. the same heat as

D. none of these

Answer 20

A

Question 21

73. A sinusoidal alternating current has a maximum value of Im. Its average value will be ______.

A. Im/π

B. Im/2π

C. 2Im/π

D. none of these

Answer 21

C

Question 22

74. The area of a sinusoidal wave over a half-cycle is ______

A. max. value /2

B. 2 x max. value

C. max. value /π

D. max. value /2π

Answer 22

B

Question 23

75. An alternating voltage is given by v = 200 sin 314t. Its r.m.s. value will be ______

A. 100 V

B. 282.8 V

C. 141.4 V

D. 121.4 V

Answer 23

C

Question 24

76. The r.m.s. value of sinusoidally varying current is _____ that of its average value.

A. more than

B. less than

C. same as

D. none of these

Answer 24

A

Question 25

77. Alternating voltages and currents are expresses in r.m.s. values because ______ A. they can be easily determined B. calculations become very simple C. they give comparison with d.c. D. none of these

Answer 25

C

Question 26

78. The average value of sin2θ over a complete cycle is ______ A. +1 B. -1 C. ½ D. zero

Answer 26

C

Question 27

79. The average value of sinθ over a complete cycle is ______. A. zero B. +1 C. -1 D. ½

Answer 27

A

Question 28

80. An alternating current is given by i = Im sin θ. The average value of squared wave of this current over a complete cycle is ______ A. Im/2 B. Im/π C. 2Im/π D. 2Im

Answer 28

A

Question 29

81. The form factor a sinusoidal wave is ______ A. 1.414 B. 1.11 C. 2 D. 1.5

Answer 29

B

Question 30

82. The filament of a vacuum tube requires 0.4 A d.c. to heat it. The r.m.s. value of a.c. required is ______. A. 0.4 x √2 B. 0.4 /2 A C. 0.8 /√2 D. 0.4 A

Answer 30

D

Question 31

83. A 100 V peak a.c. is as effective as ______ d.c. A. 100 V B. 50 V C. 70.7 V D. none of these

Answer 31

C

Question 32

84. The form factor of a ______ wave is 1. A. sinusoidal B. square C. triangular D. saw tooth

Answer 32

B

Question 33

85. Out of the following ______ wave is the peakiest. A. sinusoidal B. square C. rectangular D. triangular

Answer 33

D

Question 34

86. The peak factor of a sine wave form is ______. A. 1.11 B. 1.414 C. 2 D. 1.5

Answer 34

B

Question 35

87. When a 15-V square wave is connected across a 50-V a.c. voltmeter, it will read ______. A. 15 V B. 15 x √2 C. 15 /√2 D. none of these

Answer 35

A

Question 36

88. The breakdown voltage of an insulation depends upon _____ value of alternating voltage. A. average B. r.m.s. C. peak D. twice the r.m.s.

Answer 36

C

Question 37

89. The peak factor of a half-wave rectified a.c. is ______. A. 1.57 B. 2 C. 1.11 D. 1.4142

Answer 37

B

Question 38

90. The form factor of a half-wave rectified a.c. is ______ . A. 2 B. 1.11 C. 1.414 D. 1.57

Answer 38

D

Question 39

91. When 200 V sinusoidal peak-to-peak is connected across an a.c. voltmeter, it will read ______ A. 141.4 V B. 50 V C. 70.7 V D. none of these

Answer 39

C

Question 40

94. The average value of a sinusoidal current is 100 A. Its r.m.s value is ______. A. 63.7 A B. 70.7 A C. 141.4 A D. 111 A

Answer 40

D

Question 41

95. A current wave is given by i = 4 + 2√2 sin 3θ + 4√2 sin 5θ. The r.m.s. value of current wave is ______. A. 10 A B. 6 A C. √56 A D. 5 A

Answer 41

C

Question 42

98. An alternating voltage or current is a ______. A. scalar quantity B. vector quantity C. phasor D. none of these

Answer 42

C

Question 43

99. Three parallel circuits take the following currents: i1 = 5 sin 314t, i2 = 30 sin (314t + π/2) and i3 = 25 sin (314t – π/2). The expression for the resultant current is ______. A. 25 sin (314t + π/3) B. 5 sin (314t + π/2) C. 10 sin (314t – π/6) D. 5√2 sin (314t + π/4)

Answer 43

D

Question 44

100. The sum of the following two e.m.f’s will be ______ e1 = 10 sin ωt e2 = 10 cos ωt A. 10 B. 20 sin ωt C. 14.14 cos ωt D. 14.14 sin (ωt + π/4)

Answer 44

D