Objective Type Questions for SSC JE Electrical

61. In general, if a sine wave is fed into a Schmitt trigger, the output will be

(a) a triangular wave
(b) a square wave
(c) a saw-tooth wave
(d) an amplified sine wave

62. In the given circuit the function of the diode D is

(a) to clip the output voltage
(b) to protect the base-emitter junction
(c) to hold the output voltage to a constant value
(d) to bias the transistor

63. FET are

(a) bipolar devices
(b) either unipolar or bipolar
(c) None of these
(d) unipolar devices

64. In the circuit forward resistance of the diode D is 2 ohms and its reverse resistance is infinitely high A list consists of meters (List-I) and another list shows, the meter readings (List-II)

Which one of the options given here is correct to indicate the type of meter (List-I) and its reading (List-II)

(a) (i) –> (b), (ii) –> (a)
(b) (i) –> (a), (ii) –> (c)
(c) (i) –> (b), (ii) –> (d)
(d) (i) –> (a), (ii) –> (b)

Answer: (a) (i) ® (b), (ii) ® (a)

65. In the figure. D in an ideal diode. If the rms value of the input voltage is 50V, then the rms current through 100 ohms is

(a) 0.5 √2A
(b) 0.5 /√2
(c) 0.25
(d) 0.5 A

66. Which of the following materials is a semiconductor?

(a) Silica
(b) Chromium
(c) Selenium
(d) Bismuth

67. In a rectifier circuit, the primary function of the filter is to

(a) suppress odd harmonics in the rectifier output
(b) control the DC level the output voltage
(c) remove ripples from the rectified output
(d) minimise AC input variations

68. In an R-L series circuit R = 20 Ω, L = 0.056 H and the supply frequency in f = 50 Hz. The magnitude of impedance of the circuit is

 (a) 20.056 Ω  
(b) 26.64 Ω
(c) 20.0 Ω  
(d) 37.6 Ω

69. A pure sinusoidal current is being rectified. For the given maximum value of sinusoidal current if rms value of half wave rectified current is 50 A, then the rms value of full wave rectification will be

(a) 70.7 A
(b) 50/π A
(c) 100/π A
(d) 100 A

Answer: (a) 70.7 A

70. Under thermal equilibrium in a pure semiconductor the ratio of the number of holes to the number of conduction electrons is

(a) 2
(b) 1/2
(c) infinity
(d) 1

72. Alternator used in hydel power station has more number of poles in it than used in thermal power station, because

(a) power generated by the alternator is less
(b) speed of the prime mover may be changed whenever required
(c) power generated by the alternator may be changed according to demand
(d) speed of its prime mover is less

73. The connected load of a comsumer is 2kW and the maximum demand is 1.5kW. The demand factor of the consumer is

(a) 0.375
(b) 1.33
(c) None of these
(d) 0.75

74. In a thyrite lightning arrester the resistance

(a) decrease linearly with the applied voltage
(b) is high at low current and low at high current
(c) is low at low current and high at high current
(d) increase linearly with the applied voltage

75. A consumer is offered the following rate of tariff. He has to pay a fixed charge of Rs. 1,000 per month and a running charge of Rs. 4.50 per unit consumed. If the consumer runs a motor load of 1kW at 0.85 power factor lagging on an average of 15 hours per day, his annual bill is

(a) Rs. 32941.88
(b) Rs. 25637.50
(c) Rs. 36637.50
(d) Rs. 40985.29

76. Glare is caused due to

(a) excessive luminance
(b) none of (a) and (d)
(c) both of (a) and (d)
(d) excessive lighting contrast in the field of vision

77. Which of the following method is suitable for heating of conducting medium?

(a) Eddy current heating
(b) Induction heating
(c) Both (a) and (b)
(d) Radiant heating

78. Furnaces used for cremation use

(a) Induction heating
(b) Dielectric heating
(c) Arc heating
(d) Resistance heating

79. In a fluorescent tube circuit high voltage surge is produced by

(a) Choke
(b) Heater
(c) Electrode
(d) Starter

80. In AC operated electromechanical contractors, the problem of chattering is eliminated by

(a) placing copper shading band on plot face of electromagnet
(b) increasing the conductor cross-section
(c) using aluminium instead of copper as conductor
(d) laminating the electromagnet core