ELECTRICAL ENGINEERING IMPORTANT MCQ-BASIC ELECTRICAL PART TWO

ANSWER KEY-Correct answer is indicated by symbol (V) in options.

HINTS-In some questions options E-HINTS is indicating the hints of answer.

53) _____at a point may be defined as equal to lines of force passing normally through a
unit cross-section at that point
A [v]) Electric intensity.
B [ ]) Magnetic flux density.
C [ ]) Electric flux.
D [ ]) None of the above.

54) Electric field intensity ( E ) at any point in an electric field is equal to
A [v]) potential gradient.
B [ ]) ( potential gradient )²
C [ ]) ( potential gradient )½
D [ ]) ( potential gradient )⅓

55) The lines of force due to charged particles are
A [ ]) always straight.
B [v]) always curved.
C [ ]) sometimes curved.
D [ ]) none of above.

56) An electric field line and an equipotential surface are
A [v]) always 90°.
B [ ]) always parallel.
C [ ]) inclined at any angle.
D [ ]) none of above.

57) The ratio of electric flux density to electric field intensity is called ......... of medium
A [ ]) permeability.
B [v]) permittivity.
C [ ]) reluctance.
D [ ]) capacitance.

58) The value of E within the field due to a point charge can be found with help of
A [ ]) Faradays law.
B [ ]) Kirchhoffs law.
C [ ]) Lenzs law.
D [v]) Coulombs law.

59) The electric field at a point situated at a distance d from straight charged conductor is
A [ ]) proportional to d.
B [v]) inversely proportional to d.
C [ ]) inversely proportional to d²
D [ ]) none of abov.

60) Which field is associated with the capacitor?
A [ ]) Magnetic.
B [v]) Electric
C [ ]) Both of (1) and (2).
D [ ]) none

61) Which of the following expression is correct for electric field strength?
A [ ]) E = πD²
B [ ]) E = πD.
C [ ]) E = D² / ε.
D [v]) E = D / ε.

62) An equipotential surface is one which has all points at _____________ potential.
A [ ]) zero.
B [ ]) different.
C [v]) same.
D [ ]) none of them.

63) When a dielectric is placed in an electric field the field strength
A [v]) decreases.
B [ ]) increases.
C [ ]) reduce to zero.
D [ ]) remain unchanged.

64) For dielectrics flux is proportional to
A [v]) potential difference between electrodes.
B [ ]) resistivity of medium.
C [ ]) rate of change of potential difference.
D [ ]) rate of change of current.

65) Electric field inside a hollow metallic charged sphere is
A [ ]) increasing towards centre.
B [ ]) decreasing towards centre.
C [v]) zero.
D [ ]) none of above.

66) Unit of electric flux density is
A [ ]) coulomb.
B [ ]) farad / meter.
C [v]) coulomb / meter²
D [ ]) weber / meter²

67) The number of Faraday tubes of flux passing through a surface in an electric field is
called
A [ ]) electric charge density.
B [ ]) electric field intensity.
C [v]) electric flux.
D [ ]) magnetic flux density.

68) The unit of electric field intensity is
A [v]) N / C.
B [ ]) N / Ampere.
C [ ]) F / m
.D [ ]) F/ m²

69) 1 Tesla =
A [ ]) 1 wb- m²
B [v]) 1 wb/ m²
C [ ]) 1 wb
D [ ]) 1 wb/m.

70) Two parallel plates are separated by a distance of d meter and voltage pap plied across
the is V volts. The field intensity is given by
A [v]) V / d.
B [ ]) V × d²
C [ ]) V²
D [ ]) V × d.

71) A conductor of length l meters moves at right angles to a uniform magnetic field of flux density B = 1.5 T. if the velocity of revolution of the conductor is 50 ms-1 then induced e.m.f. in the conductor is 75 V.
A [v]) 75 V.
B [ ]) 0 V.
C [ ]) 100 V.
D [ ]) 125 V.
E [ ]) HINTS- e = Blvsinφ (φ = π/2) e = Blv = 1.5 × 1 × 50 = 75 V magnetic field

72) The magnetism left in the iron after exciting field has been removed is known as
A [ ]) permeance.
B [v]) residual magnetism.
C [ ]) susceptance.
D [ ]) reluctance.

73) The ratio of intensity of magnetisation to the magnetising force is known as
A [ ]) relative permeability.
B [v]) susceptibility.
C [ ]) flux density.
D [ ]) none of above.

74) Which of following is the unit of magnetic flux density?
A [v]) Tesla.
B [ ]) Daraf.
C [ ]) Lumens.
D [ ]) Weber.

75) The lagging of flux density behind the applied magnetising force is known as
A [ ]) permeance.
B [ ]) flux.
C [v]) hysteresis.
D [ ]) all of these

76) Which part of magnetic path requires largest mmf
A [v]) Air gap.
B [ ]) Coil.
C [ ]) Inductance.
D [ ]) Core.

77) The attraction capacity of electromagnet will increase if the
A [ ]) core length increases.
B [ ]) core area increases.
C [v]) flux density increases.
D [ ]) flux density decreases.

78) Which of following is not a unit of flux?
A [ ]) Maxwell.
B [v]) Telsa.
C [ ]) Weber.
D [ ]) All of above.

79) Which of following circuit element stores energy in electro - magnetic field?
A [v]) Inductor.
B [ ]) Condenser.
C [ ]) Variable Resistor
D [ ]) Capacitor.

80) Emf induced in a coil rotating in a uniform magnetic field will be maximum when the
A [ ]) flux linking with the coil is maximum.
B [ ]) rate of change of flux linkage is minimum.
C [v]) rate of change of flux linkage is maximum.
D [ ]) rate of cutting flux by coil sides is minimum.

81) An emf of 16 volts is induced in a coil of inductance 4 H. The rate of change of current
must be
A [ ]) 64 A / s.
B [ ]) 32 A / s.
C [ ]) 16 A / s.
D [v]) 4 A / s.

82) Conductance of any conductor is expressed as
A [ ]) ampere / watt.
B [v]) mho.
C [ ]) volt² / watt.
D [ ]) watt / ampere²

83) Three element having conductance G1, G2 and G3 are connected in parallel. Their
combined conductance will be
A [ ]) ( G1 + G2 + G3 )⁻¹
B [v]) G1 + G2 + G3.
C [ ]) 1 / G1 + 1 / G2 + 1 / G3.
D [ ]) ( 1 / G1 + 1 / G2 + 1 / G3) ⁻¹

84) Pure metal generally have
A [ ]) high conductivity and low temperature coefficient.
B [v]) high conductivity and large temperature coefficient.
C [ ]) low conductivity and zero temperature coefficient.
D [ ]) low conductivity and high temperature coefficient.

85) If the three colour bands of a resistor are grey, violet and gold, what is the value of the resistor?
A [ ]) 6.7 ohms
B [v]) 8.7 ohms.
C [ ]) 7.7 ohms
D [ ]) 9.7 ohms.
E [ ]) HINTS- The values of these colours are 8, 7 and multiplier of 0.1. Therefore, the value of  resistance will be ( 87 X 0.1 ) = 8.7 ohms.

86) A circuit contains two unequal resistor in parallel
A [v]) voltage drops across both are same.
B [ ]) currents in both are same.
C [ ]) heat losses in both are same.
D [ ]) voltage drops are according to their resistive value.

87) If the length of a wire of resistance R is uniformly stretched to n times its original value,what will be its new resistance
A [v]) n²R.
B [ ]) R / n²
C [ ]) n²/R
D [ ]) nR .
E [ ]) HINTS-Length of the conductor becomes n times and at the same time cross section of the conductor becomes 1 / Nth times. Hence resistance of the conductor becomes n² times of its original value as length of the conductor is directly proportional and cross section is inversely proportional to the resistance.

88) Two equal resistors R connected in series across a voltage source V dissipate power P.What would be the power dissipated in the same resistors when they are connected in parallel across the same voltage source ?
A [ v]) 4P.
B [ ]) P.
C [ ]) 2P.
D [ ]) 16P.
E [ ]) HINTS-Say R is the resistance of the identical two resistors. When they are connected in series across a voltage source V, the equivalent resistance of the combination is 2R and then total power dissipated by the resistors will be P = V² / 2R. When they are connected in parallel across the same voltage source V, the equivalent resistance of the combination is R/2 then total power dissipated by the resistors will be V² / ( R / 2) = 4V² / 2R = 4P.

89) he ratio of the resistance of a 200 W, 230 V lamp to that of a 100 W, 115 V lamp will be
A [ ]) 0.5.
B [v]) 2.
C [ ]) 4.
D [ ]) 0.25.

90) Three 3 Ω resistors are connected to form a triangle. What is the resistance between any two of the corner?
A [ ]) 9 Ω.
B [ ]) 6 Ω.
C [ ]) 3 Ω.
D [v]) 2 Ω.
E [ ]) HINTS-Whenever we look at the said triangle from any two of its corners, we will find that it is just a parallel combination of one 3 Ω and one 6 Ω (3 + 3 = 6) resistor. Thus, the resistance across these two corner points of the triangle will be ( 3 X 6 )/ ( 3 + 6 ) = 18 / 9 = 2 Ω.

91) A wire of resistance R has it length and cross - section both doubled. Its resistance will become
A [ ]) 0.5R
B [v]) R.
C [ ]) 2R.
D [ ]) 4R.
E [ ]) HINTS-The resistance of a conductor is directly proportional to its length and inversely proportional to its cross - sectional area. As the length and cross - sectional area both have become double, there will no change in resistance of the wire.

92) Resistance of which material does not change with change in temperature ?
A [ ]) Platinum.
B [v]) Metal alloys constantan and manganin.
C [ ]) Brass.
D [ ]) Tungsten.

93) Which of the following lamp has least resistance ?
A [v]) 200 W, 220 V.
B [ ]) 100 W, 220 V
C [ ]) 60 W, 220 V.
D [ ]) 25 W, 220 V.
E [ ]) HINTS-Resistance R=V²/W
Where, V is supply voltage and W is wattage rating of the lamp. From, above equation it is clear that, for fixed voltage source , resistance of an electric lamp is inversely proportional to its wattage rating. Here, 200 W, 220 V lamp has highest wattage rating, therefore its resistance will be least.

94) Purpose of using capacitor is / are
A [ ]) increase p.f of inductive load circuit.
B [ ]) to do phase split in AC 1 phase motor.
C [ ]) effect DC filter in electronic circuit.
D [v]) all of these.

95) The unit of capacitance is
A [v]) Farad.
B [ ]) Coulomb.
C [ ]) Henry.
D [ ]) Weber.

96) Three 60 W bulbs are in parallel across the 60 V power line. If one bulb burns open
A [ ]) there will be heavy current in the main line.
B [ ]) rest of two bulbs will not light.
C [ ]) all three bulbs will light
D [v]) the other two bulbs will light.

97) The filament of an electric bulb is made of
A [ ]) carbon.
B [ ]) nickel.
C [ ]) aluminium.
D [v]) tungsten.

98) Which of the following quantities remain the same in all parts of a parallel circuit
A [ ]) current.
B [v]) voltage.
C [ ]) resistance.
D [ ]) power.

99) When resistance element of a heater fuses and then we reconnect it after removing a
portion of it, the power of heater will
A [ ]) decrease
B [v]) increase.
C [ ]) remain constant.
D [ ]) none of these.
E [ ]) HINTS-If we remove a portion of resistance in that initial resistance, then the current resistance value will be decreased. This leads to flow more current than the previous case.Hence, according to the power equation (P = VI), if current increases then the power of the heater also increases.

100) Three identical resistors are first connected in parallel and then in series. The
resultant resistance of the first combination to the second will be
A [ ]) 9 times.
B [v]) 1 / 9 times.
C [ ]) 3 times.
D [ ]) 1 / 3 times.
E [ ]) HINTS-If we connect three identical resistors, R in parallel, then the equivalent resistance is [ R / 3]. If we add that three [ R ] resistances in series, then the equivalent resistance is [ 3R ].Now the resultant resistance of the first combination to the second will be [ R / 3 ] / 3R = [ 1 / 9].
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