250+ TOP MCQs on Cathode Ray Tube and Answers

Electrical Measurements & Measuring Instruments Multiple Choice Questions on “Cathode Ray Tube”.

1. Electron gun section ________
a) provides sharp beam
b) provides poorly focussed beam
c) doesn’t provide any beam
d) provides electrons only

Answer: a
Clarification: In a cathode ray tube, the electron gun section gives a sharply focussed beam of electrons. They are focussed on the fluorescent coated screen.

2. Control grid is given ________
a) positive voltage
b) negative voltage
c) neutral voltage
d) zero voltage

Answer: b
Clarification: Grid controls the amount of electrons falling on the fluorescent screen of a cathode ray tube. Cathode ray tube is provided with a negative voltage with respect to the cathode as a reference.

3. What determines light intensity in a CRT?
a) voltage
b) current
c) momentum of electrons
d) fluorescent screen

Answer: c
Clarification: Momentum of the electrons gives the intensity or brightness of the light emitted from the fluorescent screen due to electron bombardment. It is given as the product of the no of electrons and their speed.

4. Effect of negative voltage to the grid is ________
a) no force
b) a gravitational force
c) an attractive force
d) a repulsive force

Answer: d
Clarification: Since the electron is negatively charged, application of a negative voltage to the control grid produces a repulsive force.

5. Electron beam diverges.
a) True
b) False

Answer: a
Clarification: Similar charges on electrons lead to a repulsion. As a result the electron beam diverges as it contains many electrons. Electrostatic force is applied between the focussing anodes in order to compensate the repulsive force.

6. Focusing and accelerating anodes are ________
a) rectangular
b) cylindrical
c) spherical
d) square

Answer: b
Clarification: Focussing and accelerating anodes in a cathode ray tube are essentially cylindrical in nature. Each electrode has a small opening at the centre with a co-axial tubular axis.

7. Deflection system of a CRT consists of ________
a) 4 plates
b) 6 plates
c) 2 plates
d) 8 plates

Answer: c
Clarification: Cathode ray tube consists of two sets of plates that are parallel in nature. They are referred to as horizontal and vertical deflection plates. One of the plates is set to ground potential.

8. Horizontal deflection is given by ________
a) x = K_x
b) x = V_x
c) x = 1
d) x = K_x V_x

Answer: d
Clarification: In a cathode ray tube the horizontal deflection is given by,
x = K_x V_x
where, K_x is the constant of proportionality
x is the horizontal deflection
V_x is the horizontal deflecting voltage.

9. Vertical deflection is given by ________
a) y = K_y V_y
b) y = K_y
c) x = 1
d) y = V_y

Answer: a
Clarification: In a cathode ray tube the vertical deflection is given by,
y = K_y V_y
where, K_y is the constant of proportionality
y is the vertical deflection
V_y is the vertical deflecting voltage.