MCQ in Vacuum Tubes Part 2 | ECE Board Exam

(Last Updated On: August 10, 2018)

MCQ in Vacuum Tubes Part 2 | ECE Board Exam

This is the Multiples Choice Questions Part 2 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

Continue Practice Exam Test Questions Part 2 of the Series

Choose the letter of the best answer in each questions.

51. Which can be used for proper high frequency amplification?

A. Triode

B. Tetrode

C. Pentode

D. Diode

View Answer:

Answer: Option C

Solution:

52. The indirectly heated cathode of the diode is coated with

A. thoriated tungsten

B. nickel

C. carbon

D. strontium or barium oxide

View Answer:

Answer: Option D

Solution:

53. What started the conduction in a cold cathode tube?

A. Thermionic emission

B. Natural sources

C. Secondary emission

D. Thermal sources

View Answer:

Answer: Option B

Solution:

54. Which emitter is most commonly used in the tubes of a radio receiver?

A. Tungsten

B. Oxide coated

C. Thoriated tungsten

D. Constantan

View Answer:

Answer: Option B

Solution:

55. What is the real measure of valve’s amplification capability?

A. Plate resistance

B. Transconductance

C. Amplification factor

D. Gain

View Answer:

Answer: Option B

Solution:

56. Field emission is utilized in the mechanism of

A. vacuum tubes

B. gas-filled tubes

C. mercury pool devices

D. TV picture tubes

View Answer:

Answer: Option C

Solution:

57. A vacuum tube is normally operated in the temperature saturation region.

A. To protect against filament aging

B. To keep the tube envelope hot

C. To disperse the space charge

D. Keep the tube envelope cold

View Answer:

Answer: Option A

Solution:

58. Plate saturation results when

A. filament voltage is too high

B. space-charge region is depleted

C. plate temperature is too low

D. space-charge region is saturated

View Answer:

Answer: Option B

Solution:

59. When the control grid of a triode is operated with positive potential with respect to cathode

A. the grid resistance decreases

B. the grid may overheat

C. the plate current decreases sharply

D. the grid resistance increases

View Answer:

Answer: Option A

Solution:

60. What is the solid state equivalent of cold cathode diode?

A. Zener diode

B. LED

C. Varactor

D. Photodiode

View Answer:

Answer: Option A

Solution:

61. The nose in a gas-filled tube is ______________ that of a vacuum tube.

A. the same as

B. less than

C. more than

D. very much smaller than

View Answer:

Answer: Option C

Solution:

62. What is the phase difference of the output and input voltage of a grounded-cathode amplifier?

A. 90°

B. 360°

C. 270°

D. 180°

View Answer:

Answer: Option D

Solution:

63. A grid controlled vacuum tube acts as

A. an amplifier

B. a controlled switch

C. a rectifier

D. an oscillator

View Answer:

Answer: Option A

Solution:

64. The filament voltage is a direct measure of

A. filament temperature

B. amplification

C. plate temperature

D. filament resistance

View Answer:

Answer: Option A

Solution:

65. The equation that defines the ac plate resistance of a vacuum tube?

A. ∆Eb/∆Ec

B. ∆Ib/∆Ec

C. ∆Eb/∆Ib

D. ∆Ec/∆Ib

View Answer:

Answer: Option C

Solution:

66. The transconductance of a pentode is ____________ a triode.

A. more than that of

B. about the same as for

C. less than that of

D. not comparable to that of

View Answer:

Answer: Option B

Solution:

67. The electrons emitted by a thermionic emitter are called

A. free electrons

B. thermionic electrons

C. loose electrons

D. bound electrons

View Answer:

Answer: Option B

Solution:

68. The unit of work function of metals.

A. Joules

B. Watt-hour

C. Electron-volt

D. Watt

View Answer:

Answer: Option C

Solution:

69. What is the typical operating temperature of an oxide coated cathode?

A. 750°

B. 500°

C. 1200°

D. 1000°

View Answer:

Answer: Option A

Solution:

70. What is the amount of additional energy required to emit an electron from the surface of a metal?

A. Surface barrier

B. Threshold level

C. Work function

D. Potential

View Answer:

Answer: Option C

Solution:

71. Oxide coated emitters have electron emission of __________ per watt of heated power.

A. 5-10 A

B. 50-100 A

C. 50-150 mA

D. 150-1000 mA

View Answer:

Answer: Option D

Solution:

72. What is the pentagrid converter?

A. A tube with a total of five electrodes

B. A tube with a total of five grids

C. A tube that can be used for frequency conversion

D. A tube that requires twice as such plate voltage as a single triode

View Answer:

Answer: Option B

Solution:

73. Which emission is most widely used in practice?

A. Field

B. Secondary

C. Thermionic

D. Photo

View Answer:

Answer: Option C

Solution:

74. What is the work function of an oxide coated cathode?

A. 4.0 electron-volts

B. 2.63 electron-volts

C. 4.52 electron-volts

D. 1.1 electron-volts

View Answer:

Answer: Option D

Solution:

75. A directly heated cathode has ___________ warm-up time

A. zero

B. large

C. small

D. very large

View Answer:

Answer: Option A

Solution:

76. Which thermionic emitter has the highest opening temperature?

A. Oxide coated

B. Tungsten

C. Thoriated-tungsten

D. Eureka

View Answer:

Answer: Option B

Solution:

77. The internal resistance after ionization of a gas-filled tube is

A. low

B. very high

C. high

D. zero

View Answer:

Answer: Option A

Solution:

78. One advantage of a mercury vapor diode over the high rectifier is

A. its higher peak inverse voltage rating

B. its reduced RF interference effect

C. its lower voltage drop when the plate current is flowing

D. the elimination of the need for a warm up period

View Answer:

Answer: Option C

Solution:

79. The screen grid is used to

A. increase the capacitance between the second grid and the plate

B. decrease the capacitance between the control grid and the plate

C. reduce the secondary emission effect

D. lower the tube’s plate resistance

View Answer:

Answer: Option B

Solution:

80. A tube tester is used to check a triode’s transconductance, which is the ratio of

A. a small change in cathode current to the corresponding small change in grid current

B. a small change in plate current to the corresponding small change in grid current

C. a small change in plate voltage to the corresponding small change in plate current

D. a small change in plate voltage to the corresponding small change in plate current

View Answer:

Answer: Option B

Solution:

81. Which emitter is used in high voltage (>10 kV) applications?

A. Tungsten

B. Oxide coated

C. Thoriated-tungsten

D. Constantan

View Answer:

Answer: Option A

Solution:

82. Which of the following is a desirable characteristic of an emitter?

A. Large work function

B. Small work function

C. Very large work function

D. Very small work function

View Answer:

Answer: Option B

Solution:

83. When a thyratron tube has fired one thing that will cause it to stop conducting is

A. a more positive on the plate

B. a more negative voltage on the control electrode

C. a more positive voltage on the control electrode

D. a negative voltage on the plate

View Answer:

Answer: Option D

Solution:

84. Secondary emission effects are undesirable in

A. vacuum tubes

B. gas-filled tubes

C. ICs

D. transistors

View Answer:

Answer: Option A

Solution:

85. What would cause the plate current to increase in a pentode tube?

A. A short circuit between the plate and the screen grid

B. An open circuit in the lead that is connected to the

C. A short circuit between the suppressor grid and the cathode

D. A short circuit between the control grid and the cathode

View Answer:

Answer: Option A

Solution:

86. In directly heated cathode, filament and cathode are

A. separated components

B. same components

C. made of metals

D. made of alloys

View Answer:

Answer: Option B

Solution:

87. What is provided by transformer coupling?

A. Impedance matching

B. Step-up in voltage

C. Good frequency response

D. Stability of gain

View Answer:

Answer: Option A

Solution:

88. What is one advantage of a pentode tube over a triode?

A. Lower input impedance

B. Lower output impedance

C. Less noise internally generated

D. Less control grid to plate capacitance

View Answer:

Answer: Option D

Solution:

89. The load resistance R in a triode amplifier should be nearly _____________ for good amplification.

A. ½ rp

B. 3 rp

C. rp

D. 2 rp

View Answer:

Answer: Option B

Solution:

90. A voltage amplifier is designed to have

A. high µ and RL

B. low µ and high RL

C. high rp and low RL

D. high µ and low RL

View Answer:

Answer: Option A

Solution:

91. What transformer secondary voltage is utilized in a center-tap circuit?

A. One-half

B. One-third

C. full

D. One-eighth

View Answer:

Answer: Option A

Solution:

92. Class C amplifiers are used as ____________ amplifiers.

A. audio-frequency voltage

B. radio-frequency

C. audio-frequency power

D. audio-frequency current

View Answer:

Answer: Option B

Solution:

93. The typical application of a cold cathode tube is as a

A. diode

B. tetrode

C. triode

D. pentode

View Answer:

Answer: Option A

Solution:

94. Vacuum tube rectifiers are ___________ affected by the changes in temperatures.

A. not

B. highly

C. greatly

D. severely

View Answer:

Answer: Option A

Solution:

95. The internal resistance of a gas-filled tube is __________ that of a vacuum tube.

A. the same as

B. less than

C. more than

D. dependent

View Answer:

Answer: Option B

Solution:

96. The ionization potential in a gas diode depends upon

A. plate current

B. size of the tube

C. cathode construction

D. type and pressure of gas

View Answer:

Answer: Option D

Solution:

97. When the gas pressure in a gas-filled diode is increased, its PIV rating

A. remains unchanged

B. decreases

C. increases

D. becomes infinite

View Answer:

Answer: Option B

Solution:

98. Ionization of cold cathode diode takes place at __________ plate potential compared to hot cathode gas diode.

A. the same

B. much lower

C. much higher

D. zero

View Answer:

Answer: Option C

Solution:

99. A cold cathode diode is used as _________ tube.

A. a rectifier

B. a regulating

C. a power-controlled

D. an amplifying

View Answer:

Answer: Option B

Solution:

100. For a conventional vacuum tube used in the UHF band

A. The electron transit time becomes critical

B. The distance between the control grid and the plate must be increased

C. The physical size of the tube must be increased

D. Only a pentode can be used because of noise effects

View Answer:

Answer: Option A

Solution:

101. Ionization current which is a positive-ion current produced by collision between electrons and residual gas molecules in an electron tube is also called

A. gas current

B. gas discharge

C. plasma current

D. plasma discharge

View Answer:

Answer: Option A

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 2 | ECE Board Exam
5 (100%) 1 vote

Add Comment

© 2014 PinoyBIX Engineering. © 2018 All Rights Reserved | How to Donate?
mcq in computer fundamentals
➡️ MCQ in Computer Fundamentals Series | ECE Board Exam
mcq in industrial electronics
➡️ MCQ in Industrial Electronics Series | ECE Board Exam
MCQ in Power Generators (Cells and Batteries) Part 5 | ECE Board Exam
➡️ MCQ in Power Generators, Sources, Principles, Applications Series | ECE Board Exam
mcq in electrical circuit
➡️ MCQ in Electrical Circuit Series | ECE Board Exam

Get FREE Review Course
in your inbox

Subscribe to our mailing list and get reviewers and updates to your email inbox.

Thank you for subscribing.

Something went wrong.