MCQ in Vacuum Tubes Part 1 | ECE Board Exam

(Last Updated On: August 10, 2018)

MCQ in Vacuum Tubes Part 1 | ECE Board Exam

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

View Answer:

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

View Answer:

Answer: Option A

Solution:

3. A vacuum diode can be used as

A. an amplifier

B. an oscillator

C. a rectifier

D. a regulator

View Answer:

Answer: Option C

Solution:

4. Which generates the least noise in operation?

A. Triode valve

B. Tetrode valve

C. Pentode valve

D. Octode valve

View Answer:

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

View Answer:

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

View Answer:

Answer: Option C

Solution:

7. A vacuum diode can be used as

A. an amplifier

B. an oscillator

C. a rectifier

D. a regulator

View Answer:

Answer: Option C

Solution:

8. Which tube generates the greatest noise?

A. Triode

B. Tetrode

C. Pentode

D. Diode

View Answer:

Answer: Option C

Solution:

9. Before ionisation, a gas- filled tube has a _____________ resistance.

A. very high

B. very small

C. small

D. zero

View Answer:

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

View Answer:

Answer: Option A

Solution:

11. What emitter is used in X-ray tubes?

A. Thoriated tungsten

B. Oxide-coated

C. Tungsten

D. Nickel

View Answer:

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

View Answer:

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

View Answer:

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

View Answer:

Answer: Option C

Solution:

15. What is the solid state equivalent of thyratron?

A. FET

B. SCR

C. BJT

D. UJT

View Answer:

Answer: Option B

Solution:

16. The grid to palate capacitance is least in _________ valve

A. triode

B. tetrode

C. pentode

D. diode

View Answer:

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

View Answer:

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

View Answer:

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

View Answer:

Answer: Option C

Solution:

20. Which of the following defines the amplification factor of a vacuum tube?

A. ∆Eb/∆Ec

B. ∆Ib/∆Eb

C. ∆Ec/∆Eb

D. ∆Eb/∆Ic

View Answer:

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

View Answer:

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

View Answer:

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

View Answer:

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

View Answer:

Answer: Option C

Solution:

25. What is the typical value of ac plate resistance for a triode?

A. 1000 Ω

B. 100 kΩ

C. 1000 kΩ

D. 10 Ω

View Answer:

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

View Answer:

Answer: Option A

Solution:

27. A vacuum diode acts as a rectifier because of its ___________ conduction.

A. unidirectional

B. bidirectional

C. isotropic

D. omnidirectional

View Answer:

Answer: Option A

Solution:

28. Directly heated cathode require ___________ amount of heating

A. very small

B. large

C. small

D. very large

View Answer:

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

View Answer:

Answer: Option D

Solution:

30. What operation results in severest distortion?

A. Class C

B. Class B

C. Class A

D. Class AB

View Answer:

Answer: Option A

Solution:

31. What is the typical plate efficiency of Class A amplifier?

A. 50 %

B. 75 %

C. 30 %

D. 10 %

View Answer:

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

View Answer:

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

View Answer:

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

View Answer:

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

View Answer:

Answer: Option A

Solution:

36. A vacuum tube is a ____________ device.

A. linear

B. exponential

C. non-linear

D. bilateral

View Answer:

Answer: Option C

Solution:

37. What is the unit of transconductance?

A. Ohm

B. Siemen/m

C. Volt

D. Siemen

View Answer:

Answer: Option D

Solution:

38. Which provides the best frequency response?

A. Transformer coupling

B. RC coupling

C. Direct coupling

D. Impedance coupling

View Answer:

Answer: Option C

Solution:

39. Voltage amplifiers are operated as __________ amplifiers.

A. Class A

B. Class B

C. Class C

D. Class AB

View Answer:

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

View Answer:

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

View Answer:

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

View Answer:

Answer: Option C

Solution:

43. A thyratron can be used as

A. an oscillator

B. a controlled switch

C. an amplifier

D. an attenuator

View Answer:

Answer: Option B

Solution:

44. A pentode is a __________ device.

A. constant current

B. linear

C. constant voltage

D. bilateral

View Answer:

Answer: Option A

Solution:

45. The actual voltage gain of a triode amplifier is less than µ 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

View Answer:

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

View Answer:

Answer: Option B

Solution:

47. Which valve has the lowest amplification factor?

A. Triode

B. Pentode

C. Tetrode

D. Diode

View Answer:

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

View Answer:

Answer: Option B

Solution:

49. Valves in a radio receiver generally employ _________ heated cathodes.

A. directly

B. indirectly

C. oxide

D. nickel

View Answer:

Answer: Option B

Solution:

50. A vacuum diode acts as a ____________ switch.

A. bidirectional

B. unidirectional

C. controlled

D. omnidirectional

View Answer:

Answer: Option B

Solution:

Questions and Answers in Vacuum Tubes

Following is the list of multiple choice questions in this brand new series:

MCQ in Vacuum Tubes
PART 1: MCQs from Number 1 – 50                        Answer key: PART I
PART 2: MCQs from Number 51 – 100                   Answer key: PART II

Complete List of MCQs in Electronics Engineering per topic

MCQ in Vacuum Tubes Part 1 | ECE Board Exam
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