MCQs on Cathode Ray Oscilloscope (CRO)

The Cathode Ray Oscilloscope (CRO) is an essential tool used in electrical and electronics engineering for visualizing and analyzing electrical signals. The CRO is widely used to measure voltage, frequency, phase shifts, and time-varying signals, making it a crucial instrument in various applications, such as signal testing, waveform analysis, and troubleshooting electronic circuits. It is especially relevant for students preparing for competitive exams like SSC JE, RRB JE, GATE, and other engineering-related exams. Understanding the working principles, components, and applications of the CRO is vital for mastering its usage and performing well in exams.In this set of multiple-choice questions (MCQs), we cover various topics related to the working, construction, and applications of the CRO. These questions are designed to test your understanding of the Cathode Ray Oscilloscope and its components, including the electron gun, deflection plates, CRT screen, Lissajous patterns, and trigger circuits. The questions also examine practical aspects like bandwidth, rise time, deflection sensitivity, and the use of the CRO in measuring voltage, current, and phase differences.
  • By reviewing and answering these MCQs, you can solidify your understanding of the CRO, which will help you succeed in exams and practical applications.

  • The value of unknown current in CRO is measured by:

    • a) Ratio of voltage measured on CRO to resistance of the CRO

    • b) Ratio of voltage measured on CRO to standard resistance

    • c) Ratio of voltage measured on CRO to resistance of Aquadag

    • d) Ratio of voltage measured across the unknown resistance to that unknown resistance itself
      Answer: b) Ratio of voltage measured on CRO to standard resistance

  • A signal applied to a CRO has a rising time of 0.5 μs. Its bandwidth is:

    • a) 0.7 MHz

    • b) 0.05 MHz

    • c) 0.07 MHz

    • d) 0.2 MHz
      Answer: a) 0.7 MHz

  • A Lissajous pattern is used to measure:

    • a) Voltage and frequency

    • b) Frequency and Phase shift

    • c) Frequency and amplitude distortion

    • d) Amplitude and flux
      Answer: b) Frequency and Phase shift

  • What is the purpose of the trigger circuit in a Cathode Ray Oscilloscope (CRO)?

    • a) To generate the electron beam

    • b) To synchronize the horizontal and vertical deflections

    • c) To control the power supply circuit

    • d) To amplify the input signal
      Answer: b) To synchronize the horizontal and vertical deflections

  • The bandwidth of a CRO is the range of frequencies over which gain of:

    • a) Horizontal amplifier is within 3 dB of the mid-band frequency gain

    • b) Horizontal amplifier is within 5 dB of the mid-band frequency gain

    • c) Vertical amplifier is within 3 dB of the mid-band frequency gain

    • d) Vertical amplifier is within 5 dB of the mid-band frequency gain
      Answer: c) Vertical amplifier is within 3 dB of the mid-band frequency gain

  • The horizontal amplifier should be designed for:

    • a) High frequency signals with a fast rise time

    • b) Low amplitude signals with a fast rise time

    • c) High amplitude signals with a fast rise time

    • d) High amplitude signals with a slow rise time
      Answer: a) High frequency signals with a fast rise time

  • With respect to measuring the current in a circuit using the CRO, which of the following statements is/are correct?

    • a) Only I and II

    • b) Only III and IV

    • c) Only IV

    • d) Only I and IV
      Answer: a) Only I and II

  • How does the input impedance of a CRO affect its deflection sensitivity?

    • a) Lower input impedance leads to higher deflection sensitivity

    • b) It is directly proportional at low input impedance and inversely proportional at high input impedance

    • c) The input impedance does not affect deflection sensitivity

    • d) Higher input impedance leads to higher deflection sensitivity
      Answer: a) Lower input impedance leads to higher deflection sensitivity

  • The CRT screen is coated with phosphor, which absorbs kinetic energy of electrons and converts it into light. This process is known as:

    • a) Incandescence

    • b) Fluorescence

    • c) Luminance

    • d) Coalescence
      Answer: b) Fluorescence

  • In a cathode ray tube, the length of the deflecting plate in the direction of the beam is 2 cm, the spacing of the plate is 0.5 cm, and the distance of the fluorescent screen from the center of the plate is 18 cm. Calculate deflection sensitivity if the anode voltage is 400 V.

    • a) 0.09 cm/volt

    • b) 0.9 cm/volt

    • c) 0.18 cm/volt

    • d) 0.018 cm/volt
      Answer: a) 0.09 cm/volt

  • If the phase difference between two signals is 180°, then the Lissajous pattern will be:

    • a) An ellipse with major axis in 2nd and 3rd quadrants

    • b) A straight line with major axis in 2nd and 4th quadrants

    • c) An ellipse with major axis in 1st and 4th quadrants

    • d) A circle with major axis in 1st and 4th quadrants
      Answer: b) A straight line with major axis in 2nd and 4th quadrants

  • The signal frequency in a CRO is:

    • a) Less than 1 MHz

    • b) More than 1 MHz

    • c) More than 10 MHz

    • d) More than 10 Hz
      Answer: c) More than 10 MHz

  • What frequency does the sinusoidal signal have that occupies five horizontal divisions and three vertical divisions on a CRO for a full cycle if the time base is set to 1 ms per division?

    • a) 1 KHz

    • b) 250 Hz

    • c) 100 Hz

    • d) 200 Hz
      Answer: d) 200 Hz

  • In which of the following values are period and frequency, respectively, specified in a CRO measurement?

    • a) Seconds/cycle and cycles/period

    • b) Seconds/cycle and cycles/second

    • c) Period/cycle and cycles/second

    • d) Cycles/second and seconds/cycle
      Answer: b) Seconds/cycle and cycles/second

  • Trigger pulses in CRO are used to:

    • a) Generate high voltage required for CRT

    • b) Synchronize the input with the time base generator

    • c) Synchronize the input and vertical amplifier

    • d) Generate low voltage required for the CRT
      Answer: b) Synchronize the input with the time base generator

  • What should be the value of the phase shift for a Lissajous pattern to produce a perfect circle, if two AC signals with the same frequency are passed to the CRO?

    • a) 0 degrees

    • b) 45 degrees

    • c) 90 degrees

    • d) 180 degrees
      Answer: c) 90 degrees

  • The technique of adding a precise amount of time between the trigger point and the beginning of the scope sweep in a CRO is known as:

    • a) Free running sweep

    • b) Delayed sweep

    • c) Triggered sweep

    • d) Non-sawtooth sweep
      Answer: b) Delayed sweep

  • The rise time of a signal applied to a CRO is 0.5 μs. What is its bandwidth?

    • a) 0.05 MHz

    • b) 0.7 MHz

    • c) 0.07 MHz

    • d) 0.2 MHz
      Answer: b) 0.7 MHz

  • The above Lissajous pattern is observed in CRO. What is the phase difference between the applied signals?

    • a) 0°

    • b) 30° or 330°

    • c) 180°

    • d) 90° or 270°
      Answer: c) 180°

  • If a periodic signal displayed on the cathode ray oscilloscope screen has a distance of 4 cm between the beginning and the end of a cycle, and if the Time/Div. control is set to 1 msec/div., calculate the frequency of the waveform.

    • a) 1000 Hz

    • b) 400 Hz

    • c) 250 Hz

    • d) 100 Hz
      Answer: a) 1000 Hz

  • The intensity of the trace on the screen of a cathode ray oscilloscope can be controlled by varying the voltage on the:

    • a) Focusing anode

    • b) Grid

    • c) Horizontal deflection plates

    • d) Vertical deflection plates
      Answer: b) Grid

  • Find the phase difference of two signals which produces the above Lissajous figure in CRO.

    • a) 30° or 330°

    • b) 90° or 270°

    • c) 120° or 240°

    • d) 150° or 210°
      Answer: a) 30° or 330°

  • The set of horizontal and vertical lines permanently marked on the CRT screen is called:

    • a) Aquadag

    • b) Control grid

    • c) Focusing anode

    • d) Graticule
      Answer: d) Graticule

  • A conventional oscilloscope has a bandwidth of 100 MHz. The rise of the CRO is approximately:

    • a) 35 ns

    • b) 0.35 ns

    • c) 350 ns

    • d) 3.5 ns
      Answer: a) 35 ns

  • CRO (Cathode Ray Oscilloscope) CANNOT be used to measure:

    • a) Frequency

    • b) Phase

    • c) Power

    • d) Voltage
      Answer: c) Power

  • A vertical amplifier for a CRO can be designed for:

    • a) High gain

    • b) Different gain

    • c) Low gain

    • d) Constant gain
      Answer: a) High gain

  • The grid on the display screen of an oscilloscope that comprises the horizontal and vertical axes and used to visually measure waveform parameters is called:

    • a) Focus control

    • b) Graticule

    • c) Intensity control

    • d) Aquadag
      Answer: b) Graticule

  • Horizontal input to a scope is Em sin (ωt) V, vertical input to that scope is Em sin (ωt + 30°) V. What is the Lissajous pattern in that CRO?

    • a) Circle

    • b) Ellipse

    • c) Parabola

    • d) Straight line
      Answer: d) Straight line

  • A 1000 Hz sinusoidal voltage is connected to both X and Y inputs of a CRO. Which of the following waveforms is seen on the CRO?

    • a) Sine wave

    • b) Circle

    • c) Ellipse

    • d) Straight line
      Answer: b) Circle

  • The instrument used to measure current is called:

    • a) Wattmeter

    • b) Ohm meter

    • c) Energy meter

    • d) CRO
      Answer: d) CRO

  • In CRO, during retrace time the electron beam travels ______ from ______ of the screen.

    • a) Diagonally, top left to bottom right

    • b) Vertically, top to bottom

    • c) Horizontally, right to left

    • d) Vertically, bottom to top
      Answer: c) Horizontally, right to left

  • When two sinusoidal voltages of equal frequency but with 90° phase displacement are applied to the horizontal and vertical plates of a CRO, then the pattern appearing on the screen is:

    • a) A circle

    • b) A straight line

    • c) A parabola

    • d) An ellipse
      Answer: a) A circle

  • The connecting probe in CRO causes:

    • a) Loading

    • b) Distortion in the wave

    • c) Loading and distortion in the wave both

    • d) None of these
      Answer: c) Loading and distortion in the wave both

  • Which element in CRO is used to collect secondary emission electrons?

    • a) Deflection plates

    • b) Aquadag

    • c) Graticules

    • d) Phosphor screen
      Answer: b) Aquadag

  • The purpose of synchronizing control in a CRO is to:

    • a) Focus the spot on the screen

    • b) Lock the display of the signal

    • c) Adjust the amplitude of display

    • d) Control the intensity of the spot
      Answer: b) Lock the display of the signal

  • Calculate the fastest rise time (in ms) a sine wave can have to be reproduced by a CRO, if the bandwidth ranges from 0 Hz to 10 Hz.

    • a) 17.5

    • b) 0.35

    • c) 35

    • d) 1.75
      Answer: c) 35

  • The deflection sensitivity of the CRO is 10 m/V. What is the value of deflection factor (in V/m)?

    • a) 10

    • b) 0.12

    • c) 13

    • d) 0.014
      Answer: b) 0.12

  • The temperature inside a furnace is usually measured by:

    • a) Mercury thermometer

    • b) Optical pyrometer

    • c) Alcohol thermometer

    • d) Any of the above
      Answer: b) Optical pyrometer

  • What is the phase shift (in degrees) between the signals, which is indicated by the Lissajous pattern given below?

    • a) 0°

    • b) 60°

    • c) 90°

    • d) 180°
      Answer: d) 180°

  • In an oscilloscope screen, Linear sweep signal is applied at the:

    • a) Vertical axis

    • b) Horizontal axis

    • c) Origin

    • d) Both vertical and horizontal axis
      Answer: b) Horizontal axis

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