basic electrical MCQs – Page 2

Practise focused basic electrical questions with marked answers for exam preparation and subject revision.

basic electrical Mcqs
51. Insulating materials have the function of___________?
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A. conducting very large currents

B. preventing an open circuit between the voltage source and the load

C. storing very high currents

D. preventing a short circuit between conducting wires

52. The filament of an electric bulb is made of______________?
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A. tungsten

B. carbon

C. aluminium

D. nickel

53. Two resistances Rl and Ri are connected in series across the voltage source where Rl>Ri. The largest drop will be across______________?
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A. none of them

B. Ri

C. Rl

D. either Rl or Ri

54. In a series circuit with unequal resistances______________?
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A. the lowest resistance has the highest current

B. the highest resistance has the most of the current through it

C. the lowest resistance has the highest voltage drop

D. the highest resistance has the highest voltage drop
55. Which of the following quantities consists of SI unit as WATT ?
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A. Power

B. Current

C. Charge

D. Force

56. Out of the following which is an insulating material____________?
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A. Paper

B. Copper

C. Gold

D. Silver

57. Current velocity through a copper conductor is___________?
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A. the same as propagation velocity of electric energy

B. independent of current strength

C. nearly 3 x 108 m/s

D. of the order of a few ^.s/m
58. Insulating materials have the function of______________?
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A. preventing an open circuit between the voltage source and the load

B. conducting very large currents

C. preventing a short circuit between conducting wires

D. storing very high currents

59. If P is the power of a star connected system then what will be power of an equivalent delta connected system?
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A. 3P

B. P/3

C. None of the above

D. P

60. Three 60 W bulbs are in parallel across the 60 V power line. If one bulb burns open_________________?
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A. there will be heavy current in the main line

B. rest of the two bulbs will not light

C. the other two bulbs will light

D. all three bulbs will light

61. A closed switch has a resistance of_____________?
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A. about 50 ohms

B. zero

C. about 500 ohms

D. infinity

62. Which quantity should be measured by the voltmeter ?
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A. Current

B. Power

C. Speed

D. Voltage
63. The resistance of a copper wire 200 m long is 21 Q. If its thickness (diameter) is 0.44 mm, its specific resistance is around_______________?
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A. 1.8 x 10?8 Q-m

B. 1.6 x 10?8 Q-m

C. 1.2 x 10~8 Q-m

D. 1.4 x 10~8 Q-m

64. Capacitor does not allow the sudden change of ?
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A. None of the above

B. power

C. current

D. voltage
65. If a parallel circuit is opened in the main line, the current_______________?
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A. is zero in all branches

B. increases in the branch of the lowest resistance

C. increases in each branch

D. is zero in the highest resistive branch

66. Copper wire of certain length and resistance is drawn out to three times its length without change in volume, the new resistance of wire becomes__________?
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A. 9 times

B. 1/9 times

C. unchanged

D. 3 times

67. When resistance element of a heater fuses and then we reconnect it after removing a portion of it, the power of the heater will___________?
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A. remain constant

B. none of the above

C. decrease

D. increase
68. Bulbs in street lighting are all connected in_____________?
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A. series

B. parallel

C. series-parallel

D. end-to-end

69. are the materials having electrical conductivity much less than most of the metals but much greater than that of typical insulators______________?
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A. Thermistor

B. Variable resistors

C. Semi-conductors

D. Varistors

70. Switching of a lamp in house produces noise in the radio. This is because switching operation produces________?
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A. arcs across separating contacts

B. mechanical noise of high intensity

C. both mechanical noise and arc between contacts

D. none of the above

71. For testing appliances, the wattage of test lamp should be_____________?
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A. any value

B. low

C. very low

D. high
72. Which of the following can have negative temperature coefficient _____________?
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A. Metallic alloys

B. Liquid metals

C. Compounds of silver

D. Electrolytes
73. A thermistor has_____________?
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A. zero temperature coefficient

B. positive temperature coefficient

C. negative temperature coefficient

D. variable temperature coefficient

74. Whether circuit may be AC. or D. C. one, following is most effective in reducing the magnitude of the current?
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A. Capacitor

B. Resistor

C. Inductor

D. Reactor

75. When one leg of parallel circuit is opened out the total current will______________?
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A. become zero

B. reduce

C. decrease

D. increase

76. A nichrome wire used as a heater coil has the resistance of 2 2/m. For a heater of 1 kW at 200 V, the length of wire required will be_____________?
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A. 60 m

B. 80 m

C. 40 m

D. 20 m
77. Voltage dependent resistors are used_____________?
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A. for inductive circuits

B. to supress surges

C. as heating elements

D. as current stabilizers

78. 74. Sparking occurs when a load is switched off because the circuit has high_________?
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A. inductance

B. resistance

C. capacitance

D. impedance

79. Resistance of a material always decreases if___________?
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A. number of free electrons available become more

B. temperature of material is decreased

C. temperature of material is increased

D. none of the above is correct

80. Nichrome wire is an alloy of_____________?
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A. copper and silver

B. lead and zinc

C. nickel and chromium

D. chromium and vanadium

81. Conductance : mho :: ____________?
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A. capacitance : henry

B. inductance : farad

C. resistance : ohm

D. lumen : steradian

82. A glass rod when rubbed with silk cloth is charged because__________?
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A. it takes in proton

B. it gives away positive charge

C. its atoms are removed

D. it gives away electrons
83. International ohm is defined in terms of the resistance of________________?
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A. the unit length of wire

B. a cube of copper

C. a cube of carbon

D. a column of mercury
84. Two lamps 100 W and 40 W are connected in series across 230 V (alternating). Which of the following statement is correct ?
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A. 100 W lamp will glow brighter

B. 40 W lamp will glow brighter

C. Both lamps will glow equally bright

D. 40 W lamp will fuse

85. A field of force can exist only between_____________?
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A. two metal particles

B. two molecules

C. two atoms

D. two ions
86. The thickness of insulation provided on the conductor depends on_____________?
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A. the magnitude of voltage on the conductor

B. the magnitude of current flowing through it

C. both A. and (b)

D. none of the above

87. A 40 W bulb is connected in series with a room heater. If now 40 W bulb is replaced by 100 W bulb, the heater output will__________
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A. increase

B. remain same

C. decrease

D. heater will burn out

88. In the case of direct current____________?
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A. magnitude and direction of current remains constant

B. magnitude and direction of current changes with time

C. magnitude of current remains constant

D. magnitude of current changes with time

89. Two copper conductors have equal length. The cross-sectional area of one conductor is four times that of the other. If the conductor having smaller cross-sectional area has a resistance of 40 ohms the resistance of other conductor will be_____________?
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A. 160 ohms

B. 80 ohms

C. 20 ohms

D. 10 ohms
90. If/, R and t are the current, resistance and time respectively, then according to Joules law heat produced will be proportional to_______________?
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A. I2R2t

B. I2Rf

C. I2R2t*

D. I2Rt
91. Which of the following quantities remain the same in all parts of a series circuit ____________?
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A. Current

B. Voltage

C. Power

D. Resistance

92. Temperature co-efficient of resistance is expressed in terms of___________?
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A. ohms/C

B. mhos/ohmC

C. mhos/C

D. ohms/ohmC
93. The insulation on a current carrying conductor is provided__________?
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A. to prevent leakage of current

B. to prevent shock

C. both of above factors

D. none of above factors

94. It becomes more difficult to remove_________________?
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A. third electron from the orbit

B. any electron from the orbit

C. second electron from the orbit

D. first electron from the orbit

95. Ohms law is not applicable to__________?
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A. small resistors

B. D. C. circuits

C. semi-conductors

D. high currents

96. In a lamp load when more than one lamp are switched on the total resistance of the load_____________?
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A. remains same

B. increases

C. decreases

D. none of the above

97. A substance whose molecules consist of dissimilar atoms is called____________?
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A. compound

B. super-conducto

C. semi-conductor

D. insulator

98. Which of the following statement is correct_______________?
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A. A semi-conductor is a material whose conductivity is same as between that of a conductor and an insulator

B. A semi-conductor is a material made of alternate layers of conducting material and insulator

C. A semi-conductor is a material which has conductivity having average value of conductivity of metal and insulator

D. A semi-conductor is one which conducts only half of the applied voltage

99. When electric current passes through a metallic conductor, its temperature rises. This is due to__________?
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A. mutual collisions between metal atoms

B. mutual collisions between conducting electrons

C. the release of conduction electrons from parent atoms

D. collisions between conduction electrons and atoms
100. When current flows through heater coil it glows but supply wiring does not glow because______________?
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A. current through supply line flows at slower speed

B. supply wires are made of superior material

C. resistance of heater coil is more than the supply wires

D. supply wiring is covered with insulation layer