This is the Multiples Choice Questions Part 1 of the Series in Vacuum Tubes as one of the Electronics Engineering topic. In Preparation for the ECE Board Exam make sure to expose yourself and familiarize in each and every questions compiled here taken from various sources including but not limited to past Board Exam Questions in Electronics Engineering field, Electronics Books, Journals and other Electronics References.
Multiple Choice Questions Topic Outline
- MCQ in Vacuum Tubes
Start Practice Exam Test Questions Part 1 of the Series
Choose the letter of the best answer in each questions.
1. What are the two principal electrodes in every tube?
A. Plate and control grid
B. Cathode and screen grid
C. Plate and cathode
D. Screen grid and control grid
Answer: Option C
Solution:
2. For a given plate voltage, if negative potential on the control grid of triode is increased, the plate current
A. decreases
B. remains the same
C. increases
D. becomes zero
Answer: Option A
Solution:
3. A vacuum diode can be used as
A. an amplifier
B. an oscillator
C. a rectifier
D. a regulator
Answer: Option C
Solution:
4. Which generates the least noise in operation?
A. Triode valve
B. Tetrode valve
C. Pentode valve
D. Octode valve
Answer: Option A
Solution:
5. A vacuum tube will conduct only if its plate is ______________ with respect to the cathode.
A. positive
B. negative
C. at zero potential
D. at infinite potential
Answer: Option A
Solution:
6. Saturation in a tube is a condition where an increase in plate voltage will produce
A. a rise in electron emission
B. a decrease in electron emission
C. no appreciable change in plate current
D. an appreciable change in plate current
Answer: Option C
Solution:
7. A vacuum diode can be used as
A. an amplifier
B. an oscillator
C. a rectifier
D. a regulator
Answer: Option C
Solution:
8. Which tube generates the greatest noise?
A. Triode
B. Tetrode
C. Pentode
D. Diode
Answer: Option C
Solution:
9. Before ionisation, a gas- filled tube has a _____________ resistance.
A. very high
B. very small
C. small
D. zero
Answer: Option A
Solution:
10. The negative resistance characteristics of the tetrode is due to
A. secondary emission
B. plate being positive with respect to cathode
C. control grid being negative with respect to cathode
D. screen grid being negative with respect to cathode
Answer: Option A
Solution:
11. What emitter is used in X-ray tubes?
A. Thoriated tungsten
B. Oxide-coated
C. Tungsten
D. Nickel
Answer: Option C
Solution:
12. When the temperature of an emitter is increased two times, the electron emission
A. increases two times
B. increases four times
C. increases several million times
D. decreases two times
Answer: Option C
Solution:
13. What is the typical life span of an oxide coated emitter?
A. 500 hours
B. 200 hours
C. 1000 hours
D. 10000 hours
Answer: Option D
Solution:
14. The cathode heating time of thermionic glass diode is ___________ that of a vacuum diode.
A. the same as
B. much less than
C. much more than
D. not related to
Answer: Option C
Solution:
15. What is the solid state equivalent of thyratron?
A. FET
B. SCR
C. BJT
D. UJT
Answer: Option B
Solution:
16. The grid to palate capacitance is least in _________ valve
A. triode
B. tetrode
C. pentode
D. diode
Answer: Option C
Solution:
17. The peak inverse voltage of a diode is defined as the maximum allowable
A. negative voltage across the load resistor
B. negative voltage applied to plate with respect to cathode
C. positive voltage to plate with respect to cathode
D. positive voltage applied across the load resistor
Answer: Option B
Solution:
18. The equation that defines the dc plate resistance of a vacuum tube.
A. Eb/Ib
B. Ib2 x Eb
C. Ib x Eb
D. Ib/Eb
Answer: Option A
Solution:
19. The voltage on the suppressor grid of a pentode is generally
A. positive with respect to cathode
B. positive with respect to cathode
C. zero with respect to cathode
D. at zero potential
Answer: Option C
Solution:
20. Which of the following defines the amplification factor of a vacuum tube?
A. โEb/โEc
B. โIb/โEb
C. โEc/โEb
D. โEb/โIc
Answer: Option A
Solution:
21. Which is the best tube for high frequency amplification?
A. Triode valve
B. Tetrode valve
C. Pentode valve
D. Diode valve
Answer: Option C
Solution:
22. A triode is normally operated with control grid at ___________ potential with respect to cathode.
A. positive
B. high positive
C. zero
D. negative
Answer: Option D
Solution:
23. Once a thyratron is fired, its control grid ____________ over palate current.
A. loses all control
B. exercises rough control
C. exercises fine control
D. becomes helpless
Answer: Option A
Solution:
24. The ____________ voltage should be reduced to zero to stop conduction in a thyratron.
A. grid
B. filament
C. plate
D. heater
Answer: Option C
Solution:
25. What is the typical value of ac plate resistance for a triode?
A. 1000 โฆ
B. 100 kโฆ
C. 1000 kโฆ
D. 10 โฆ
Answer: Option A
Solution:
26. Direct coupling is used for ___________ amplification.
A. very low frequency
B. radio-frequency
C. audio-frequency
D. ultra high frequency
Answer: Option A
Solution:
27. A vacuum diode acts as a rectifier because of its ___________ conduction.
A. unidirectional
B. bidirectional
C. isotropic
D. omnidirectional
Answer: Option A
Solution:
28. Directly heated cathode require ___________ amount of heating
A. very small
B. large
C. small
D. very large
Answer: Option C
Solution:
29. A hard tube is defined as a tube with
A. a tungsten filament
B. a gas in the envelope
C. a metal envelope
D. no gas in the envelope
Answer: Option D
Solution:
30. What operation results in severest distortion?
A. Class C
B. Class B
C. Class A
D. Class AB
Answer: Option A
Solution:
31. What is the typical plate efficiency of Class A amplifier?
A. 50 %
B. 75 %
C. 30 %
D. 10 %
Answer: Option C
Solution:
32. For the sample plate dissipation, the output power of a Class B push-pull circuit is nearly ___________ that of Class A operation.
A. 2 times
B. 4 times
C. 3 times
D. 5 times
Answer: Option D
Solution:
33. The screen grid potential is kept ____________ plate potential
A. somewhat lower than
B. same as
C. somewhere higher than
D. at zero potential with respect to
Answer: Option A
Solution:
34. The output stage of a practical amplifier always employs what coupling?
A. RC coupling
B. Transformer coupling
C. Direct coupling
D. Impedance coupling
Answer: Option B
Solution:
35. The plate resistance of a tube is mainly due to
A. space charge
B. electrodes of the tube
C. vacuum in the tube
D. gas in the tube
Answer: Option A
Solution:
36. A vacuum tube is a ____________ device.
A. linear
B. exponential
C. non-linear
D. bilateral
Answer: Option C
Solution:
37. What is the unit of transconductance?
A. Ohm
B. Siemen/m
C. Volt
D. Siemen
Answer: Option D
Solution:
38. Which provides the best frequency response?
A. Transformer coupling
B. RC coupling
C. Direct coupling
D. Impedance coupling
Answer: Option C
Solution:
39. Voltage amplifiers are operated as __________ amplifiers.
A. Class A
B. Class B
C. Class C
D. Class AB
Answer: Option A
Solution:
40. The PIV of hot cathode gas diode is ___________ the equivalent vacuum diode.
A. the same as that of
B. less than
C. more than
D. independent that of
Answer: Option B
Solution:
41. The anode-cathode potential of a gas-filled tube at which gas de-ionizes and stops conduction is called __________ potential.
A. extinction
B. ionizing
C. striking
D. reverse
Answer: Option A
Solution:
42. For the same plate voltage, a gas diode can conduct ____________ the equivalent vacuum diode.
A. less current than
B. same current as
C. more current than
D. one-half the current than
Answer: Option C
Solution:
43. A thyratron can be used as
A. an oscillator
B. a controlled switch
C. an amplifier
D. an attenuator
Answer: Option B
Solution:
44. A pentode is a __________ device.
A. constant current
B. linear
C. constant voltage
D. bilateral
Answer: Option A
Solution:
45. The actual voltage gain of a triode amplifier is less than ยต due to
A. grid being negative with respect to cathode
B. voltage drop in ac resistance of the tube
C. plate being positive with respect to cathode
D. voltage drop in dc resistance of the tube
Answer: Option B
Solution:
46. For faithful amplification, the control grid should be __________ with respect to cathode.
A. positive
B. negative
C. at zero potential
D. at infinite potential
Answer: Option B
Solution:
47. Which valve has the lowest amplification factor?
A. Triode
B. Pentode
C. Tetrode
D. Diode
Answer: Option A
Solution:
48. Which of the following would have the most effect on decreasing the life of a vacuum tube?
A. Too much of a grid excitation
B. An excessive filament voltage
C. A grid current that is too low
D. A plate resistance value that is too high
Answer: Option B
Solution:
49. Valves in a radio receiver generally employ _________ heated cathodes.
A. directly
B. indirectly
C. oxide
D. nickel
Answer: Option B
Solution:
50. A vacuum diode acts as a ____________ switch.
A. bidirectional
B. unidirectional
C. controlled
D. omnidirectional
Answer: Option B
Solution:
Questions and Answers in Vacuum Tubes
Following is the list of multiple choice questions in this brand new series:
Complete List of MCQs in Electronics Engineering per topic
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