Questions for class 12 physics to get good mark in board exams NCERT Class 12 physics Important Questions with Answers Important 1 Mark Questions for Class 12 Physics to Get Good Mark
1. The least doped region in transistor is
(a) emitter
(b) collector
(C) base
(d) either emitter or collector
(e) either collector or base
2. When the conductivity of a semiconductor is only Elso due to breaking of co-valent bonds, the semiconductor is called:
(a) intrinsic sox4 nil
(D) extrinsic
(d) n-type
(c) p-type
3. In common base configuration I, = mA 0.95, the value of base current is
(a) 1.95 mA to
(b) 0.05 mA
(c) 1.05 mA101oub
(d) 0.95 mA
4. The impurity atom with which pure silicon should be doped to make a p-type semiconductor are those of :
(b) antimony
(a) phosphorous
(d)arsenic
(c) boron
5. In a p-n junction:
(a) high potential at side and low at p side
(b) high potential at side and low at n side
(c) p and n both at same potential
(d) undetermined
6. When arsenic is added as an impurity to silicon the resulting material is:
(a) n-type conductor
(b) n-type semiconductor
(C) p-type conductor
(d) p-type semiconductor
7. The p-n junction diode works as insulator if Connected
(a) to AC
(b) in forward bias
(d) none of these
(C) in reverse bias
8.When the resistance between p and then plate is high then the p-n junction
(b) capacitor
(a)resistor
(c) transistor
(d) none of these
9.The resistance of reverse biased p-n junction diode is about:
(a) 1 ohm
(b) 10 ohms
(c) 100 ohms
(d) 110 ohms
10. The diffusion current in a p-n junction is
(a) from to p
(b) from p to n
(c) from n to p if forward biased
(d) from p to n if reverse biased
11.Impurity atom making n-type semiconductor is
(a) trivalent
(6) tetravalent
(c) pentavalent
(d) hexavalent
12. An intrinsic semiconductor has
(a) free electron in excess
(b) holes in excess
(c) no free electrons and holes.
(d) equal number of free electrons and holes.
13. Ap-type semiconductor has
(a) free electron in excess
(b) free holes in excess
(c) no free electrons and holes.
(d) equal number of free electrons and holes.
14. An n-type semiconductor has
(a) free electrons in excess t t
(b) free holes in excess
(c) no free electrons and holes.
(d) equal number of free electrons and holes.
15. At absolute zero, an intrinsic semiconductor has
(a) free electrons in excess
(b) free holes in excess
(c) no free electrons and holes
(d) equal number of free electrons and holes.
16. With rise in temperature conductivity of conductor
(b) decreases
(a) increases
(d)zero
(c) infinite
17. With rise in temperature conductivity of A semiconductors
(b) decreases
(a) increases
(d) zeroE0
(c) infinite
18. Metallic bodies are
(b) transparent
(a) opaque
(d) none of these
(c) both
19. Transparent bodies are
(b) insulators
(a) conductors
(d) none of these
(c) both
20. In semiconductor diode, depletion layer is formed
(a) at outer end of p-type
(b) at outer end of n -type
(c) at the p-n junction
(d) nowhere.
21. In current conduction through p-type semiconductor
(a) electrons flow inside and holes flow outside.
(b) holes flow inside as well as outside.
(c) holes flow inside and electron flow outside.
(d) electrons flow inside as well as outside.
22. In current conduction through N-type semiconductor
(a) electrons flow inside and holes flow outside.
(b) holes flow inside and electrons flow outside.
(c) holes flow inside as well as outside.
(d) electrons flow inside as well as outside.
23. Depletion layer has
(a) free electrons only(b) free holes only
(c) both (a) and (b) (d) none of these
24. With a forward bias, the width of depletion layer
(d) increases
(a) decreases
(c) first increases then decreases
(d) neither increases nor decreases.
25. With a reverse bias, the width of depletion lay er
(b) increases
(a) decreases
(c) first increases then decreases
(d) neither increases nor decreases.
26.In p-type semiconductor minority carriers are.
(a)both free electrons and holes. o
(b)neither free electrons nor holes,
(c) free electrons only.
(d) free holes only,
27.In n-type semiconductor, minority carriers are
(a) both free electrons and holes
(b) neither free electrons nor holes
(c) free electrons only.
(d) holes only
28.With reverse bias, current is due to
(a) minority carriers only
(b) majority carriers only
(c) both (a) and (b) (d) none of these.
29.With forward bias, the order of the junction resistance is
(a) 12
(b) 10 Q
(c)100 2
(d)10000 2
30.With reverse bias, the order of the junction resistance is
(a)1 €
(b)10 2
(c) 100 2
(d) 10000 2
31. Crystalline solids are____in nature.
(a) Anisotropic
(6) Isotropic
(c) Both
(d)None of these
32.Which of the following is amorphous solid?
(a) Glass
(b) Sugar
(c) Diamond
(d)None of these
33. The crystal in which regularity of atoms or molecules extend over the entire crystal is known as
(a) Single crystal
(b)Poly crystal
(d) None of these
(c) Liquid crystal
34. The range of energies possessed by an electron in a solid is called VA
(b)Valence band
(a) Energy band
(c)Conduction band
(d) None of these
35. The current gain of a transistor in common base mode is 0.99. Emitter current is Sm A, what is collector current?
(b) 2.45 mA
(a) 0.196 mA
(d) 5.1 mA
(c) 4.95 mA
36. Most of the solids are __
(a) open
(b)Close
(C) cristalline
(d) mad
39. In comparision to a half-wave rectifier, a full wave rectifier gives lower
(a) efficiency
(b) average d.c.
(c) average output voltage
(d) none of these
38. Transistors are
(a) electron sensitive device
(b) pressure sensitive device
(c)holes sensitive device
(d) temperature sensitive device
39. On increasing the reverse bias to a large value in p-n junction, the diode current
(b) increases slowly
(a) remains fixed
(c) decreases slowly
(d) suddenly increases
40.What is the voltage gain in CE mode amplifier. when input resistance is 32 and resistance is 242 and B= 60?
(b) 2.4
(a) 8.4
(d) 4.8
(c) 480
41. In half wave rectifier, frequency of applied voltage is 50 Hz. Frequency of rectified current ripple will be
(b) 25 Hz
(a) 10 Hz
(d)100 Hz
(c) 50 Hiz
42. In full wave rectifier, ripple frequency will be
(6) 25 Hz
(a) 10 Hz
(d) 100 Hz
(c) 50 Hz
43. In a transistor, the most doped section is
(a) emittor
(b) base
(d) none.
(c) collector
44. In a transistor, the thinnest section is
(b) base
(a) emmiter
(d) none
(c) collector
45. A transistor transforms
(b) voltage
(a) current
(d) resistance
(c) power
46. In common-emitter amplifier, current gain is
(b) zero
(a) less than one
(d) infinite.
(c) more than one
47. In a common-emitter amplifier, the output and input have a phase difference
b)180
(a) 27
(d) 0P
(c) 90
48. A n rectifier converts
(b) D.c. to A.c
(a) a.c to D.c
(c) both (a) and (b)
(d) none.
ANSWERS
1. (c) 2. (a)3. (b) 4. (c) 5. (a)6. (b) 7. (c)8. (b) 9. (d) 10. (b)11. (c) 12. (d) 13. (b) 14. (a) 15. (c) 16. (b) 17. (a) 18. (a) 19. (b) 20. (c) 21. (c) 22. (d) 23. (d) 24. (a) 25. (b) 26. (c) 27. (d) 28. (a) 29.(b) 30. (d) 31. (a) 32. (a)33. (a) 34. (a) 35.(c) 36. (c)38 (d) 39. (d) 40. (c) 37. (c)41. (c) 42.(d) 43. (a) 44. (b) 45. (d)46. (c) 47. (b) 48. (a)