In this section of Electronic Devices and Circuits.It contain Vacuum Tubes MCQs (Multiple Choice Questions Answers).All the MCQs (Multiple Choice Question Answers) requires in depth reading of Electronic Devices and Circuits Subject as the hardness level of MCQs have been kept to advance level.These Sets of Questions are very helpful in Preparing for various Competitive Exams and University level Exams.
This Section covers below lists of topics :
- Electron Emission,Method of electron Emission,Thermal emission MCQs.
- Thermal emitters MCQs.
- Secondary Emissions MCQs.
- Photo electric emission MCQs
- Vacuum tube,vacuum diode MCQs
- Characteristics of vacuum diode MCQ
- Vacuum Triode ,vacuum triode as an amplifier MCQs
- Vacuum tetrode MCQs
- Vacuum Pentode MCQs
Practice it now to sharpen your concept.
PRACTICE IT NOW TO SHARPEN YOUR CONCEPT AND KNOWLEDGE
1. The principle method of electron emission
- Thermodynamic and secondary emission
- Field and secondary emission
- Thermodynamic and photoelectric emission
- B and C both
D. B and C both
2. Depending upon the type of emitter, the temperature used for thermionic emission varies is between
- 0 to 200k
- 100 to 800k
- 1050 to 2600 k
- 300 to 26000 k
C. 1050 to 2600 k
3. The most commonly used emitter in receiving tube is
- Oxide coated
- Thoriated tungsten
- Tungsten
- None of these
A. Oxide coated
4. For the emission of free electron, the energy supplied to it must be
- less than work function
- equal to work function
- equal to or more than work function
- none of these
C. equal to or more than work function
5. the work function of an oxide coated emitter is
- 2.63 eV
- 2.1 eV
- 4.52 eV
- 1.0 eV
D. 1.0 eV
6. The substance having lower work function will emit electrons at
- Room temperature
- lower temperature
- higher temperature
- all of these
B. lower temperature
7. The valves used in radios employ
- Indirectly heated cathode
- directly heated cathode
- indirectly heated cathode
- directly heated cathode
A. Indirectly heated cathode
8. Oxide coated emitter are used when plate voltages
- less than 500 volt
- nearly 2000 volt
- 1000 V or more than this
- none of these
A. less than 500 volt
9. The principal properties of cathode material are
- Low work function and high mechanical strength
- High melting point and high mechanical strength
- Low work function, high melting point and high mechanical strength
- low work function, low melting point and high mechanical strength
C. Low work function, high melting point and high mechanical strength
10. The emission of electrons from a metallic surface by the bombardment of high speed particles is called
- photoelectric emission
- field emission
- thermionic emission
- secondary emission
D. secondary emission
11. The two principal electrodes present in every tube are
- cathode and grid
- anode and control grid
- cathode and anode
- none of these
C. cathode and anode
12. A vacuum tube is also known as electronic valve because
- it is number of electrodes
- it conducts only in one direction
- electrodes are enclosed in evacuated envelope
- it carries electrons
B. it conducts only in one direction
13. A vacuum diode can be used as
- rectifier
- amplifier
- oscillator
- sound detector
A. rectifier
14. Vacuum tube will only conduct if its anode is kept at a positive terminal with respect to cathode
- true
- false
A. true
15. in a vacuum triode
- territory electrodes cold cathode anode and control grid
- the control grid is kept near the cathode then anode
- the control grid is always kept attractive potential with respect to cathode
- all of these
D. all of these
16. A triode is used as an amplifier because
- a small change in grid potential causes large change in plate current
- anode of the tube is kept at a positive potential
- grid is always kept at a negative potential with respect to cathode
- None of these
A. a small change in grid potential causes large change in plate current
17. Vacuum diode will conduct when
- Cathode is at - 200 volt and anode is at - 50 volt
- Cathode is at + 200 volt and anode is at - 50 volt
- Cathode is at - 200 volt and anode is at +50 volt
- both a and c
D. both a and c
18. The negative resistance characteristics of a tetrods is known as
- rectification
- dynatron effect
- amplification effect
- none of these
B. dynatron effect
19. The negative resistance characteristics of cathode is due to
- speed of electrons
- ionization
- secondary emission at anode
- electrostatic effect of suppressor grid
C. secondary emission at anode
20. The painted Valve, The suppression grid is always kept at
- zero potential
- negative potential
- positive potential
- the same potential as that of cathode
D. the same potential as that of cathode
21. Hard tube is defined as a tube with
- tungsten filament
- a metal envelope
- an evacuated glass envelope
- none of these
C. an evacuated glass envelope
22. The vacuum tubes are generally operated in the
- saturated region
- space charge Limited region
- both a and b
- none of these
B. space charge Limited region
23. The screen grid potential is
- Positive more than flat potential
- Negative Motion Control grid
- Negative less than control grid
- Positive less than plate potential
D. Positive less than plate potential
24. for the amplification of high frequency signal
- vacuum triode is used
- vacuum tetrod is used
- vacuum pentode is used
- vacuum diode is used
C. vacuum pentode is used
