VACUUM & SEMICON

Review Questions

1. A vacuum tube has electrodes confined inside an evacuated ________.

a. Glass envelope onlyb. Metal envelope onlyc. Either glass or metal envelope d. Plastic envelope

VACUUM & SEMICON

2. Calculate the velocity needed by an electron to be emitted from the surface of a tungsten material whose work function is 4.52 eV

a. 1.3 Mm/sb. 2.3 Mm/sc. 3.3 Mm/sd. 4.3 Mm/s

VACUUM & SEMICON

3. In which of the following applications vacuum tubes in a radio transmitter are used to

a. Public addressing systemb. Radio receiversc. Radio transmittersd. electroplating

VACUUM & SEMICON

4. The emission of electrons in a vacuum tube diode is achieved by

a. Electrostatic fieldb. Magnetic fieldc. heatingd. Electron bombardment

VACUUM & SEMICON

5. When an electron moves through a potential difference of 10 Volts, the energy acquired by it will be

a. 10 ergsb. 10 joulesc. 10 wattsd. 10 eV

VACUUM & SEMICON

6. Secondary emission of electrons occurs when the metal surface is

a. Cooled to very low temperatureb. heatedc. Subjected to electric as well as

magnetic fieldd. Bombardment with high energy

electrons

VACUUM & SEMICON

7. Which of the following electron emission process is widely used in vacuum tubes?

a. Photo electric emissionb. High filed emissionc. Thermionic emissiond. Secondary emission

VACUUM & SEMICON

8. Generally metals with low work function have

a. Low melting pointb. Non-crystalline structurec. High hardnessd. Low specific gravity

VACUUM & SEMICON

9. Which of the following emitter material has the lowest work function?

a. Oxide coatedb. Thoriated tungstenc. Pure tungstend. copper

VACUUM & SEMICON

10. The work function of the oxide coated emitter material is ________.

a. 1 eVb. 2.63 Vc. 3.98 eVd. 4.52 eV

VACUUM & SEMICON

11. Which of the following material usually needs less than 1000 V as plate voltage?

a. Oxide coatedb. Thoriated tungstenc. Pure tungstend. All of the above

VACUUM & SEMICON

12. In case of indirectly heated tubes, the heater filament is usually made of

a. manganinb. tungstenc. invard. gold

VACUUM & SEMICON

13. In case of indirectly heated cathode, the cathode is in the shape of ______.

a. Wire filamentb. cylinderc. Metal stripd. circular

VACUUM & SEMICON

14. The surface of the anode is usually blacked and roughened to

a. Dissipate heat produced at he anodeb. Arrest scaping electronsc. Retard fast electrons emitted by

cathoded. Eliminate outside interference

VACUUM & SEMICON

15. A control grid is provided in the pentode tube to

a. Collect electrons from the space chargeb. Control the number of electrons moving from

cathode to platec. Restrict the secondary emission from the plated. Accelerate the electron emission from the plate

VACUUM & SEMICON

16. The grid of the triode is normally maintained at _________.

a. Negative potential with respect to cathodeb. Positive potential with respect to cathodec. Zero potentiald. Same potential as that of the anode

VACUUM & SEMICON

17. What is the smallest element of a matter?

a. neutronb. electronsc. protonsd. atom

VACUUM & SEMICON

18. The definite discrete amount of anergy required to move an electron from a lower shell to a higher shell

a. quantab. Negative energyc. quantumd. Positive energy

VACUUM & SEMICON

19. What will happen to an atom if an electron is either taken out or taken into the same atom?

a. Becomes negative ionb. Becomes an ionc. Becomes positive iond. Nothing will happen

VACUUM & SEMICON

20. When an atom gains additional ______, it results to a negative ion

a. atomb. neutronc. electrond. proton

VACUUM & SEMICON

21. Amount of additional energy required for electronic emission of metals

a. electronvoltb. Work functionc. Band gapd. MeV

VACUUM & SEMICON

22. Emission of electrons from a material by application of a very high voltage

a. Secondary emissionb. Thermionic emissionc. High field emissiond. Photoelectric emission

VACUUM & SEMICON

23. Another name of vacuum tube diode

a. Fleming valveb. audionc. thyratrond. detector

VACUUM & SEMICON

24. How many electrodes does a pentode have?

a. fourb. twoc. threed. five

VACUUM & SEMICON

25. What is the gain of a vacuum tube having the following parameters; amplification factor is 80, external plate-load resistance of 30,000 ohms and the tubes internal plate resistance is 10,000 ohms?

a. 60b. 20c. 30d. 40

VACUUM & SEMICON

26. Triodes are usually rated by their

a. µb. gm

c. rp

d. Voltage gain

VACUUM & SEMICON

27. Which terminal of the tetrode is nearest to its anode?

a. Screen gridb. cathodec. Suppressor gridd. Control grid

VACUUM & SEMICON

28. Which of the VT devices is secondary emission a major problem?

a. triodeb. pentodec. tetroded. hexode

VACUUM & SEMICON

29. The _____ grid in an electron tube is where the input signal is usually applied

a. screenb. controlc. Biasd. suppression

VACUUM & SEMICON

30. A heptode tube has how many grids?

a. 7b. 1c. 5d. 3

VACUUM & SEMICON

31. ______ is a gaseous tube which uses a pool of liquid mercury as its cathode

a. thyratronb. phanatronc. klystrond. ignitron

VACUUM & SEMICON

32. Thyratrons in industrial electronics refer to _______

a. A gas-filled diodeb. A vacuum tubec. A gas-filled trioded. An electron triode

VACUUM & SEMICON

33. _____ is a low frequency oscillation which sometimes occurs under fault condition in electron tube circuits

a. Ping pongb. jitterc. glitchd. Motor boating

VACUUM & SEMICON

34. _____ are electrons at the outer shell

a. Valence electronsb. Inside the shell electronsc. Outside shell electronsd. Conductor electrons

VACUUM & SEMICON

35. A good material conductor should have ____ valence electrons

a. 21b. 10c. 1d. 3.5

VACUUM & SEMICON

36. The difference in energy between the valence and conduction bands of a semiconductor is called

a. Band gapb. Extrinsic photo effectc. conductivityd. Energy density

VACUUM & SEMICON

37. What elements posses four valence electrons?

a. insulatorsb. Semi-insulatorsc. semiconductorsd. conductors

VACUUM & SEMICON

38. What two elements wisely used in semiconductor devices that exhibit both metallic and non-metallic characteristics?

a. Galena and Germaniumb. Silicon and Goldc. Galena and Bismuthd. Silicon and Germanium

VACUUM & SEMICON

39. This happens when a free electrons returns to the valence shell

a. holeb. ionizationc. recombinationd. lifetime

VACUUM & SEMICON

40. _____ has a unit of electronvolt (eV)

a. currentb. Chargec. Energyd. Potential difference

VACUUM & SEMICON

41. The name of a pure semiconductor material that has an equal number of electrons and holes

a. N-typeb. Pure typec. intrinsicd. P-type

VACUUM & SEMICON

42. What type of material is formed when trivalent material is doped with silicon or germanium?

a. N typeb. N & P typec. PN typed. P type

VACUUM & SEMICON

43. Which is the majority carrier in an N-type semiconductor?

a. electronb. Positive ionc. Negative iond. hole

VACUUM & SEMICON

44. The in which a high velocity beam of electrons or ions is made to strike a metal surface and the impinging ions gives sufficient energy to enable them to overcome the barrier and escape.

a. Thermionic emissionb. Photoelectric emissionc. Secondary emissiond. High filed emission

VACUUM & SEMICON

45. What is the purpose of screen grid ?

a. To reduce interelectrode capacitanceb. To increase amplification factorc. To decrease secondary emission currentd. To turn off the vacuum tube

VACUUM & SEMICON

46. It is usually connected to the cathode thus having substantially negative potential to overcome the effects of the secondary emission.

a. suppressorb. screenc. controld. plate

VACUUM & SEMICON

47. Reducing the plate and screen grid voltages of an amplifier will _____ control grid cut-off voltage.

a. unstableb. increasec. Stay stabled. decrease

VACUUM & SEMICON

48. Hw do you call an eight element vacuum tube?

a. octodeb. pentodec. hexoded. heptode

VACUUM & SEMICON

49. What is the output of a100-µ VT amplifier having a load resistance of 10 kΩ, and plate resistance of 5kΩ and input of 1 Vrms?

a. 0.44Wb. 0.66µWc. 0.66Wd. 1W

VACUUM & SEMICON

50. Shell with the most number of electrons.

a. Nb. Mc. Ld. K

VACUUM & SEMICON

51. _____ is an orderly pattern of combined silicon atoms.

a. Covalent bondb. Valence orbitc. semiconductord. crystal

VACUUM & SEMICON

52. An electronic semiconductor behaves as _____ at absolute temperature.

a. A variable resistorb. A conductorc. A super conductord. An insulator

VACUUM & SEMICON

53. The amount of time between the creation of a hole and its disappearance is called

a. dopingb. lifetimec. recombinationd. Thermal energy

VACUUM & SEMICON

54. A hole in the semiconductor is defined as

a. A free electronb. An incomplete part of an electron pair

bondc. A free protond. A free neutron

VACUUM & SEMICON

55. Semiconductor whose electron and hole concentration are equal.

a. Doped semiconductorb. Extrinsic semiconductorc. Intrinsic semiconductord. Equal semiconductor

VACUUM & SEMICON

56. Arsenic and phosphorus are examples of pentavalent impurity when added to a semiconductor creates

a. Bound electronsb. Valence electronsc. Free electronsd. holes

VACUUM & SEMICON

57. Which is not a trivalent atom?

a. Alb. Bic. Ind. B

VACUUM & SEMICON

58. Which of the following refers to an electron in the conduction band?

a. Electrons driven by photonsb. Electrons that loses its charge easilyc. Those electrons with lower energy than

those in the valence bandd. Those electrons with higher energy than

those in the valence band

VACUUM & SEMICON

59. The valence electron of a copper atom experiences what kind of attraction toward the nucleus?

a. noneb. weakc. strongd. Impossible to say

VACUUM & SEMICON

60. The valence of a conductor is also called a

a. Bound electronb. Free electronc. nucleusd. proton

VACUUM & SEMICON

61. What happens to the resistance of the copper wire when it is heated?

a. increasesb. Remains the samec. decreasesd. Becomes zero

VACUUM & SEMICON

62. When the temperature of an extrinsic semiconductor increases the pronounced effect is on

a. Majority carriersb. Minority carriersc. Junction capacitanced. Majority and minority carriers

VACUUM & SEMICON

63. A semiconductor has _______ temperature coefficient of resistance.

a. negativeb. positivec. zerod. Either positive or negative