1. A vacuum tube has electrodes confined inside an evacuated________.a. Glass envelope onlyb. Metal envelope onlyc. Either glass or metal enveloped. Plastic envelope

2. Calculate the velocity needed by an electron to be emitted from the surface of a tungsten material whose work function is 4.52 eVa. 1.3 Mm/sb. 2.3 Mm/sc. 3.3 Mm/sd. 4.3 Mm/s

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

4. The emission of electrons in a vacuum tube diode is achieved bya. electrostatic fieldb. magnetic fieldc. heatingd. electron bombardment

5. When an electron moves through a potential difference of 10 Volts, the energy acquired by it will bea. 10 ergsb. 10 joulesc. 10 wattsd. 10eV

6. Secondary emission of electrons occurs when the metal surface isa. Cooled to very low temperatureb. heatedc. Subjected to electric as well as magnetic fieldd. Bombardment with high energy electrons

7. Which of the following electron emission process is widely used in vacuum tubes?a. Photo electric emissionb. High field emissionc. Thermionic emissiond. Secondary emission

8. Generally metals with low work function havea. Low melting pointb. Non-crystalline structurec. High hardnessd. Low specific gravity

9. Which of the following emitter material has the lowest work function? a. oxide coatedb. thoriated tungstenc. pure tungstend. copper

10. The work function of the oxide coated emitter material is _________.a. 1 eVb. 2.63 eVc. 3.98 eVd. 4.52 eV

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

12. In case of indirectly heated tubes, the heater filament is usually made ofa. manganinb. tungstenc. invard. Gold13. In case of indirectly heated cathode, the cathode is in the shape of___.a. Wire filamentb. cylinderc. Metal stripd. Circular

14. The surface of the anode is usually blacked and roughened toa. Dissipate heat produced at the anodeb. Arrest escaping electronsc. Retard fast electrons emitted by cathoded. Eliminate outside interference15. A control grid is provided in the pentode tube toa. 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

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

17. What will likely to happen when cathode of a vacuum tube is heated and the anode is not connected to any external circuit?a. Electrons escape through glass tubeb. Glass tube gets chargec. Electrons form a space charged. Protons are emitted from anode

18. A triode can also be used as an amplifier because_______.a. It has 3 elements like a transistorb. Plate is a high values and less positivec. Control grid voltage is made less negatived. Any small change in grid is capable of causing a larger change in plate voltage

19. In a cathode ray tube, which electrode has the highest positive voltage?a. cathodeb. anodec. heaterd. Control grid

20. What is the unit of amplification factor?a. siemensb. ohmsc. amperesd. Unitless

21. The value of parasitic capacitance of the triode increases as_______.a. Current increasesb. Current decreasesc. Signal frequency increasesd. Signal frequency decreases

22. The control grid of the triode is usually given negative potential with respect to the cathode so as to_______.a. Reduce the grid current to zerob. Reduce the space chargec. Increase the space charged. Restrict the space charge to a safe value

23. In a tetrode tube, secondary emissions means the emission of a. High velocity electrons from the cathodeb. Electrons from the plate due to bombardment of the fast moving electrons emitted from the cathodec. Electrons from the filament due to heat energyd. Electrons from the filament due to light energy

24. The phenomenon of secondary emission is common in_________.a. diodesb. triodesc. tetrodesd. Pentodes

25. In a pentode, the suppressor grid is provided between a. Plate and screen gridb. Cathode heaterc. Screen grid and plated. Control grid and cathode

26. In a pentode, the suppressor grid is used to_______.a. Limit anode voltageb. Limit anode currentc. Dissipate heatd. Suppress secondary emission

27. Which of the following vacuum tube cannot be used as an amplifier?a. diodeb. triodec. tetroded. Pentode

28. Which of the following does not have three electrons?a. Boronb. Aluminumc. Galliumd. Phosphorus29. What is the forbidden energy gap of germanium?a. 0.12 eVb. 1.12 eVc. 0.72 eVd. 7.2 eV

30. The forbidden energy gap between the valence band and the conduction band will be least in case of a. metalsb. semiconductorsc. Insulatorsd. All of the above

31. What is a semiconductor in its purest form?a. Intrinsic semiconductorb. Extrinsic semiconductorc. P-type materiald. N-type material

32. At absolute zero temperature, a semiconductor behaves like a. An insulatorb. A superconductorc. A conductord. A variable resistor

33. When the atoms are held together by the sharing of valence electronsa. Each atoms becomes free to moveb. Neutrons start shiftingc. They form a covalent bondd. Some of the electrons are lost

34. What happen when an electron breaks a covalent bond and move away?a. A hole is createdb. A proton is also lostc. Atom becomes an iond. Rest of the electrons moves at faster rate

35. It is the process of deliberately adding impurity to a semiconductor material is calleda. Impurificationb. Pollutionc. Deionizationd. Doping

36. What is a doped semiconductor?a. Impure semiconductorb. Dipole semiconductorc. Bipolar semiconductord. Extrinsic semiconductor

37. What are the two mechanisms by which holes and electrons move through a silicon crystal?a. Covalent bond and recombinationb. Forward and reverse biasc. Free and charge particlesd. Diffusion and drift

38. Pure silicon crystal atoms contain how many valence electrons as a result of covalent bonding?a. 2b. 4c. 8d. 16

39. What is considered as the key to electrical conductivity?a. the number of electrons in the valence orbitb. the number of neutrons in the nucleusc. the number of protons and electrons in the atomd. the number of neutrons in the nucleus

40. Lifetime is the amount of time between the creation and disappearance of a/an_______.a. free electronb. protonc. iond. neutron

41. Silicon that has been doped with a trivalent impurity is calleda. p-type semiconductorb. n-type semiconductorc. intrinsic semiconductord. extrinsic semiconductor

42. In an N-type semiconductor, holes are called_______.a. minority carriersb. majority carriersc. protonsd. charge carriers43. A silicon crystal is _______if every atom in the crystal is a silicon atom.a. extrinsic semiconductorb. intrinsic semiconductorc. p-type materiald. n-type material

44. Before doping, the semiconductor material isa. dehydratedb. heatedc. hardenedd. purified

45. Which of the following is acceptor impurity element?a. antimonyb. galliumc. arsenicd. phosphorus

46. An electrically neutral semiconductor hasa. no free chargesb. no majority carriersc. no minority carriersd. equal number of positive and negative charges

47. In an N-type semiconductor, the concentration of the minority carriers mainly depends ona. the number of acceptor atomsb. the number of doping atomsc. extent of the atomd. temperature of the material

48. The resistivity of semiconductora. increase as the temperature increasesb. decreases as the temperature increasesc. remains constant even wren the temperature variesd. remains constant even when the temperature is constant

49. Semiconductors have _________.a. zero temperature coefficientb. positive temperature coefficientc. negative temperature coefficientd. all of the above

50. What is the crystal structure of silicon?a. simple cubicb. body central cubicc. face centered cubicd. diamond