SSC JE Electrical MCQ

61. Three 3 µF capacitors are in series. A 6 µF capacitor is in parallel with this series arrangement. The equivalent capacitance of this combination is

(a) 7 µF
(b) 15 µF
(c) 3.6 µF
(d) 1 µF

62. A DC series motor has an armature resistance of 0.06 Ω  and series field resistance of 0.08 Ω. The motor is connected to a 400 V supply. Thus line current is 20 A when the speed of the machine is 1100 rpm. When the line current is 50 A and the excitation is increased by 30%, speed of the machine in rpm is

(a) 1100
(b) 1003
(c) 837
(d) 938

63. The voltage across R, L and C are 3V, 14 V, and 10 V respectively as in the figure. If the voltage source is sinusoidal, then the input voltage (rms) is

(a) 10 V
(b) 5 V
(c) 2.5 V
(d) 15 V

64. In 1-phase series RL circuit fed by voltage source, the resistance and reactance values are 4 ohm each. In this circuit.

(a) the current leads the voltage by 45°
(b) the current lags the voltage by 45°
(c) the current lags the voltage by 60°
(d) None of the above

65. Super position theorem requires as many circuits to be solved as there are

(a) nodes
(b) sources
(c) loops
(d) None of the above

66. In squirrel cage induction motor, the rotor conductors are

(a) open circuited
(b) short circuited via end rings
(c) short circuited via external reactance
(d) short circuited via external resistance

67. A 3-phase synchronous motor is started by utilizing the torque developed in

(a) the high speed steam turbine
(b) the damper winding on the rotor
(c) the damper winding on the stator
(d) the low speed water turbine

68. If the frequency of input voltage of a transformer is increased keeping the magnitude of the voltage unchanged, then

(a) both hysteresis loss and eddy current loss in the core will increase.
(b) hysteresis loss will increase but eddy current loss will decrease
(c) hysteresis loss will increase but eddy current loss will remain unchanged
(d) hysteresis loss will decrease but eddy current loss will increase

69. Two 1-phase AC motors A and B operate from a 1000 V supply. A consumes 2 kW at a power factor of 0.8 (lagging) and B comsumes 1 kW at a power factor of 0.5 (lagging). The total current drawn from the supply is approximately

(a) 4.5 A
(b) 2.1 A
(c) 4.41 A
(d) 9 A

70. The high voltage and low voltage winding resistances of a distribution transformer of 100KVA, 1100/220 V, 50 Hz are 0.1 Ω  and 0.004 Ω  respectively. The equivalent resistances referred to high voltage side and low voltage side are respectively

(a) 2.504 Ω  and 0.2 Ω
(b) 0.2 Ω  and 0.008 Ω
(c) 0.10016 Ω  and 2.504 Ω
(d) 0.008 Ω  and 0.10016 Ω

71. A tank circuit consists of

(a) an inductor and a capacitor connected in series
(b) an inductor and a capacitor connected in parallel
(c) a pure inductance and a pure capacitance connected in series
(d) a pure inductance and a pure capacitance connected in parallel

72. The instantaneous power of a 1-phase series circuit supplying R-L load from a sinusoidal voltage source has in each cycle.

(a) negative twice, zero four times
(b) zero twice, negative once
(c) negative four times, zero twice
(d) negative twice, zero once

73. In a series R-L-C circuit, the “Q-factor” is given by

74. In an ac circuit, V = (200 + j 40) V and I = (30 – j 10) A. The active and reactive power of the circuit are respectively

(a) 6400 W, 800 VAR capacitive
(b) 6400 W, 800 VAR inductive
(c) 5600 W, 3200 VAR capacitive
(d) 5600 W, 3200 VAR inductive

Answer: (d) 5600 W, 3200 VAR inductive

75. Application of Norton’s theorem in a circuit results in

(a) a current source and an impedance in paralle
(b) a voltage source and an impedance in series
(c) an ideal voltage source
(d) an ideal current source

76. 

The voltage (v) vs current (i) curve of the circuit is shown below :

Internal resistance of the source e is
(a) 24 Ω  
(b) 4 Ω
(c) 10 Ω  
(d) 14 Ω

77. Value of the load impedance Z_L for which the load consumes maximum power is

(a) 50 Ω  at a power factor of 0.6 lead
(b) 50 Ω  at a power factor of 0.6 lag
(c) 30 Ω  at a power factor of unity
(d) None of the above

78. The speed – torque characteristics of a DC series motor operating from a constant voltage supply is

80. Three equal impedances are first connected in delta across a 3-phase balanced supply. If the same impedances are connected in star across the same supply

(a) phase currents will be 1/3 of the previous value
(b) line currents will be 1/3 of the previous value
(c) power consumed will be 1/3 of the previous value
(d) power consumed will be 3 times the previous value