MCQ on Electrical Measuring Instruments with Answers

61. What is the approximate input impedance of a CRO ?

(a) Zero
(b) 1 MΩ
(c) 10 Ω
(d) 10 µΩ

62. Which one of the following measuring devices has minimum loading effect on the quantity under measurement ?

(a) PMMC.
(b) CRO.
(c) Hot wire.
(d) Electrodynamometer.

63. In CRT aquadag carries

(a) aqueous solution of graphite.
(b) sweep voltage.
(c) secondary emission electrons.
(d) none of the above.

64. The purpose of providing acquadag in CRT is to

(a) increase fluorescence.
(b) increase phosphorescence.
(c) protect burning of screen.
(d) remove electrostatic charge accumulation.

65. The Miller sweep circuit normally used in a CRO is basically

(a) a voltage to current converter circuit.
(b) a current to voltage converter circuit.
(c) an integrator circuit.
(d) a differentiator circuit.

66. In a CRO, the time-base generators supply ramp voltage to

(a) horizontal deflecting plates.
(b) vertical deflecting plates.
(c) both horizontal and vertical deflecting plates.
(d) none of the above.

67. In a CRT the highest positive potential is given to

(a) focusing electrodes.
(b) cathode
(c) vertical deflection plates.
(d) post deflection acceleration anode.

68. Post-deflection is required in CRO, if input signal frequency is

(a) less than 1 kHz.
(b) less than 1 MHz.
(c) below 10 MHz.
(d) above 10 MHz.

69. In a CRO astigmatism is

(a) a source of generating fast electrons.
(b) a medium for absorbing secondary emission electrons.
(c) an additional focus control.
(d) a time-delay control in the vertical deflection system.

70. The purpose of the synchronizing control in a CRO is to

(a) focus the spot on the screen.
(b) lock the display of signal.
(c) adjust the amplitude of display.
(d) control the intensity of the spot.

71. It is desired to make accurate measurement of voltage using a CRO. Which of the following items should be taken into consideration in this measurement ?

1. Electrostatic deflection type CRT.
2. Magnetic deflection type CRT.
3. Small deflection for measurement at the center of the screen.
4. Large deflection to cover the entire screen.

Select the correct answer using the code given below :
(a) 1 and 4.
(b) 2 and 3.
(c) 2 and 4.
(d) 1 and 3.

72. Which one of the following statements correctly represents the post acceleration in a CRT ?

(a) It provides deflection of the beam.
(b) It increases the brightness of the trace if the signal frequency is higher than 10 MHz.
(c) It accelerates the beam before deflection.
(d) It increases the brightness of the trace of low frequency signal.

73. Lissajous pattern obtained on the screen of a CRO can be used to determine

(a) phase shift.
(b) amplitude distortion.
(c) voltage amplitude.
(d) none of the above.

74. The X and Y inputs of a CRO are respectively V sin ωt and -V sin ωt. The resulting Lissajous pattern will be

(a) a straight line.
(b) a circle.
(c) an ellipse.
(d) a figure of eight.

75. The sine wave output of a function generator is fed to both the horizontal (X) and vertical (Y) inputs of a CRO. What will be the pattern on the cathode ray screen ?

(a) A circle.
(b) An ellipse.
(c) A straight line with 45° slope.
(d) Sinusoidal.

76. Two in-phase, 50 Hz sinusoidal waveforms of unit amplitude are fed into channel 1 and channel 2 respectively of an oscilloscope. Assuming that the voltage scale, time scale and other settings are exactly the same for both the channels, what would be observed if the oscilloscope is operated in X – Y mode ?

(a) A circle of unit radius.
(b) An ellipse.
(c) A parabola.
(d) A straight line inclined at 45° with respect to the x-axis.

77. Which of the following measurements can be made using Lissajous figures ?

1. Frequency
2. Phase difference
3. Time interval between pulses.
4. Pulse width.
5. Fundamental and higher harmonic components. Select the correct answer using the code given below :

(a) 1 and 2
(b) 2 and 3
(c) 3 and 4
(d) 4 and 5

 

• Electrical and Electronics Measurement Mcq – 1
• Electrical and Electronics Measurement Mcq – 2
• Electrical and Electronics Measurement Mcq – 3
• Electrical and Electronics Measurement Mcq – 4
• Electrical and Electronics Measurement Mcq – 5

©yourelectricalguide.com/ mcq on electrical measuring instruments with answers.