Title 26. SEMI CONDUCTORS and ELECTRONIC DEVICES EASY.pdf ✅

1. The nature of binding for a crystal with alternate and evenly spaced positive and negative ions is (a) Covalent (b) Metallic (c) Dipolar (d) Ionic 2. For a crystal system, a = b = c,  =  =   90o , the system is (a) Tetragonal system (b) Cubic system (c) Orthorhombic system (d) Rhombohedral system 3. Biaxial crystal among the following is (a) Calcite (b) Quartz (c) Selenite (d) Tourmaline 4. The temperature coefficient of resistance of a conductor is (a) Positive always (b) Negative always (c) Zero (d) Infinite 5. Potassium has a bcc structure with nearest neighbour distance 4.525 Å. Its molecular weight is 39. Its density in kg/m3 is (a) 900 (b) 494 (c) 602 (d) 802 6. The expected energy of the electrons at absolute zero is called (a) Fermi energy (b) Emission energy (c) Work function (d) Potential energy 7. In a triclinic crystal system (a) a  b  c ,      (b) a = b = c ,      (c) a  b  c ,    =  (d) a = b  c ,  =  =  8. Metallic solids are always opaque because (a) Solids effect the incident light (b) Incident light is readily absorbed by the free electron in a metal (c) Incident light is scattered by solid molecules (d) Energy band traps the incident light 9. In which of the following ionic bond is present (a) NaCl (b) Ar (c) Si (d) Ge 10. Which of the following materials is non crystalline (a) Copper (b) Sodium chloride (c) Wood (d) Diamond 11. The coordination number of Cu is (a) 1 (b) 6 (c) 8 (d) 12 12. Which one of the following is the weakest kind of bonding in solids (a) Ionic (b) Metallic (c) Vander Waals (d) Covalent 13. In a crystal, the atoms are located at the position of (a) Maximum potential energy (b) Minimum potential energy (c) Zero potential energy (d) Infinite potential energy 14. Crystal structure of NaCl is \ (a) Fcc (b) Bcc (c) Both of the above (d) None of the above 15. What is the coordination number of sodium ions in the case of sodium chloride structure (a) 6 (b) 8 (c) 4 (d) 12 16. The distance between the body centred atom and a corner atom in sodium (a = 4.225 Å) is (a) 3.66 Å (b) 3.17 Å (c) 2.99 Å (d) 2.54 Å 17. A solid that transmits light in visible region and has a very low melting point possesses (a) Metallic bonding (b) Ionic bonding (c) Covalent bonding (d) Vander Waal’s bonding 18. Atomic radius of fcc is (a) 2 a (b) 2 2 a (c) a 4 3 (d) a 2 3 19. A solid reflects incident light and it’s electrical conductivity decreases with temperature. The binding in this solids (a) Ionic (b) Covalent (c) Metallic (d) Molecular 20. The laptop PC’s modern electronic watches and calculators use the following for display (a) Single crystal (b) Poly crystal (c) Liquid crystal (d) Semiconductors 21. The nearest distance between two atoms in case of a bcc lattice is equal to (a) 3 2 a (b) 2 3 a
(c) q 3 (d) 2 a 22. What is the net force on a Cl– placed at the centre of the bcc structure of CsCl (a) Zero (b) 2 2 ke / a (c) 2 2 ke a (d) Data is incomplete 23. Sodium has body centred packing. If the distance between two nearest atoms is 3.7 Å, then its lattice parameter is (a) 4.8 Å (b) 4.3 Å (c) 3.9 Å (d) 3.3 Å 24. Which of the following is an amorphous solid (a) Glass (b) Diamond (c) Salt (d) Sugar 25. Copper has face centered cubic (fcc) lattice with interatomic spacing equal to 2.54Å. The value of the lattice constant for this lattice is (a) 1.27 Å (b) 5.08 Å (c) 2.54 Å (d) 3.59 Å 26. In good conductors of electricity, the type of bonding that exists is (a) Ionic (b) Vander Waals (c) Covalent (d) Metallic 27. Bonding in a germanium crystal (semi- conductor) is (a) Metallic (b) Ionic (c) Vander Waal's type (d) Covalent 28. The ionic bond is absent in (a) NaCl (b) CsCl (c) LiF (d) H2O 29. The majority charge carriers in P-type semiconductor are (a) Electrons (b) Protons (c) Holes (d) Neutrons 30. A P-type semiconductor can be obtained by adding (a) Arsenic to pure silicon (b) Gallium to pure silicon (c) Antimony to pure germanium (d) Phosphorous to pure germanium 31. In a semiconductor, the concentration of electrons is 14 3 8 10 / cm and that of the holes is 5 10 . 12 3  cm The semiconductor is (a) P-type (b) N-type (c) Intrinsic (d) PNP-type 32. In P-type semiconductor, there is (a) An excess of one electron (b) Absence of one electron (c) A missing atom (d) A donar level 33. The valence of the impurity atom that is to be added to germanium crystal so as to make it a N-type semiconductor, is (a) 6 (b) 5 (c) 4 (d) 3 34. Silicon is a semiconductor. If a small amount of As is added to it, then its electrical conductivity (a) Decreases (b) Increases (c) Remains unchanged (d) Becomes zero 35. When the electrical conductivity of a semi- conductor is due to the breaking of its covalent bonds, then the semiconductor is said to be (a) Donar (b) Acceptor (c) Intrinsic (d) Extrinsic 36. A piece of copper and the other of germanium are cooled from the room temperature to 80 K, then which of the following would be a correct statement (a) Resistance of each increases (b) Resistance of each decreases (c) Resistance of copper increases while that of germanium decreases (d) Resistance of copper decreases while that of germanium increases 37. To obtain P-type Si semiconductor, we need to dope pure Si with (a) Aluminium (b) Phosphorous (c) Oxygen (d) Germanium 38. Electrical conductivity of a semiconductor (a) Decreases with the rise in its temperature (b) Increases with the rise in its temperature (c) Does not change with the rise in its temperature Cs+ Cs+ Cs+ Cs+ Cs+ Cs Cs + + Cs+ Cl a a a
(d) First increases and then decreases with the rise in its temperature 39. Three semi-conductors are arranged in the increasing order of their energy gap as follows. The correct arrangement is (a) Tellurium, germanium, silicon (b) Tellurium, silicon, germanium (c) Silicon, germanium, tellurium (d) Silicon, tellurium, germanium 40. When a semiconductor is heated, its resistance (a) Decreases (b) Increases (c) Remains unchanged (d) Nothing is definite 41. In an insulator, the forbidden energy gap between the valence band and conduction band is of the order of (a) 1 MeV (b) 0.1MeV (c) 1eV (d) 5 eV 42. A N-type semiconductor is (a) Negatively charged (b) Positively charged (c) Neutral (d) None of these 43. The energy band gap of Si is (a) 0.70 eV (b) 1.1 eV (c) Between 0.70 eV to 1.1eV (d) 5 eV 44. The forbidden energy band gap in conductors, semiconductors and insulators are 1 2 EG , EG and EG3 respectively. The relation among them is (a) EG1 = EG2 = EG3 (b) EG1  EG2  EG3 (c) EG1  EG2  EG3 (d) EG1  EG2  EG3 45. Which statement is correct (a) N-type germanium is negatively charged and P-type germanium is positively charged (b) Both N-type and P-type germanium are neutral (c) N-type germanium is positively charged and P-type germanium is negatively charged (d) Both N-type and P-type germanium are negatively charged 46. When Ge crystals are doped with phosphorus atom, then it becomes (a) Insulator (b) P-type (c) N-type (d) Superconductor 47. Let P n and e n be the number of holes and conduction electrons respectively in a semiconductor. Then (a) P e n  n in an intrinsic semiconductor (b) P e n = n in an extrinsic semiconductor (c) P e n = n in an intrinsic semiconductor (d) e P n  n in an intrinsic semiconductor 48. Wires P and Q have the same resistance at ordinary (room) temperature. When heated, resistance of P increases and that of Q decreases. We conclude that (a) P and Q are conductors of different materials (b) P is N-type semiconductor and Q is P-type semiconductor (c) P is semiconductor and Q is conductor (d) P is conductor and Q is semiconductor 49. The impurity atoms which are mixed with pure silicon to make a P-type semiconductor are those of (a) Phosphorus (b) Boron (c) Antimony (d) Copper 50. Holes are charge carriers in (a) Intrinsic semiconductors (b)Ionic solids (c) P-type semiconductors (d)Metals 51. In extrinsic P and N-type, semiconductor materials, the ratio of the impurity atoms to the pure semiconductor atoms is about (a) 1 (b) 1 10 − (c) 4 10 − (d) 7 10 − 52. A hole in a P-type semiconductor is (a) An excess electron (b) A missing electron (c) A missing atom (d) A donor level 53. The forbidden gap in the energy bands of germanium at room temperature is about (a) 1.1eV (b) 0.1eV (c) 0.67eV (d) 6.7eV 54. In P-type semiconductor the majority and minority charge carriers are respectively (a) Protons and electrons (b) Electrons and protons (c) Electrons and holes (d) Holes and electrons 55. At zero Kelvin a piece of germanium (a) Becomes semiconductor (b) Becomes good conductor (c) Becomes bad conductor
(d) Has maximum conductivity 56. Electronic configuration of germanium is 2, 8, 18 and 4. To make it extrinsic semiconductor small quantity of antimony is added (a) The material obtained will be N-type germanium in which electrons and holes are equal in number (b) The material obtained will be P-type germanium (c) The material obtained will be N-type germanium which has more electrons than holes at room temperature (d) The material obtained will be N-type germanium which has less electrons than holes at room temperature 57. A semiconductor is cooled from T1K to . T2K Its resistance (a) Will decrease (b) Will increase (c) Will first decrease and then increase (d) Will not change 58. If N P and Ne be the numbers of holes and conduction electrons in an extrinsic semiconductor, then (a) NP  Ne (b) NP = Ne (c) NP  Ne (d) NP  Ne or NP  Ne depending on the nature of impurity 59. In intrinsic semiconductor at room temperature, number of electrons and holes are (a) Equal (b) Zero (c) Unequal (d) Infinite 60. (USS 133) Indium impurity in germanium makes (a) N-type (b) P-type (c) Insulator (d) Intrinsic 61. Fermi level of energy of an intrinsic semiconductor lies (a) In the middle of forbidden gap (b) Below the middle of forbidden gap (c) Above the middle of forbidden gap (d) Outside the forbidden gap 62. In a semiconductor the separation between conduction band and valence band is of the order of (a) 100 eV (b) 10 eV (c) 1eV (d) 0 eV 63. The intrinsic semiconductor becomes an insulator at (a) 0C (b) −100 C (c) 300 K (d) 0 K 64. The addition of antimony atoms to a sample of intrinsic germanium transforms it to a material which is (a) Superconductor (b) An insulator (c) N-type semiconductor (d) P-type semiconductor 65. Resistance of semiconductor at 0K is (a) Zero (b) Infinite (c) Large (d) Small 66. In a good conductor the energy gap between the conduction band and the valence band is (a) Infinite (b) Wide (c) Narrow (d) Zero 67. The impurity atom added to germanium to make it N-type semiconductor is (a) Arsenic (b) Iridium (c) Aluminium (d) Iodine 68. When N-type of semiconductor is heated (a) Number of electrons increases while that of holes decreases (b) Number of holes increases while that of electrons decreases (c) Number of electrons and holes remains same (d) Number of electrons and holes increases equally 69. To obtain a P-type germanium semiconductor, it must be doped with (a) Arsenic (b) Antimony (c) Indium (d) Phosphorus 70. The temperature coefficient of resistance of a semiconductor (a) Is always positive (b) Is always negative (c) Is zero (d) May be positive or negative or zero 71. P-type semiconductor is formed when A. As impurity is mixed in Si B. Al impurity is mixed in Si C. B impurity is mixed in Ge D. P impurity is mixed in Ge (a) A and C (b) A and D (c) B and C (d) B and D 72. In case of a semiconductor, which of the following statement is wrong (a) Doping increases conductivity