SOLID STATE PHYSICS

1. Which one of the following process is used to purify a soluble solid?

A. Evaporation
B. Crystallisation
C. Condensation
D. Distillation
Answer: B. Crystallisation
2. Crystals having low melting points are in
A. Vander waal's bond
B. Ionic bond
C. Covalent bond
D. Metallic bond
Answer: D. Metallic bond

3. The working of a quartz crystal in the watch is based on the

A. photo electric effect
B. Johnson effect
C. Piezo-electric effect
D. Edison effect
Answer: C. Piezo-electric effect

4. i). Graphite is an allotrope of carbon

ii). Diamond is metal
A. false, false
B. true, true
C. false, true
D. true, false
Answer: D. true, false

5. Nodes are
A. positions of maximum displacement
B. positions of no displacement
C. a position between no displacement and maximum displacement
D. None of these
Answer: B. positions of no displacement

6. The lowest level energy band in a solid is called

A. Valence band
B. conduction band C. fermi level
D. equal level
Answer : A. Valence band
7. Find the correct one
A. Conversion from the solid state to liquid state-freezing
B. conversion from the solid state to gaseous state-fusion
C. conversion from the Solid state to gaseous state- sublimation
D. conversion from the liquid state to solid state-vaporisation
Answer C. conversion from the Solid state to gaseous state- sublimation

8. Dry ice is
A. solid carbon
B. solid nitrogen
C. solid ammonia
D. solid methane
Answer A. solid carbon

9. If the temperature of an extrinsic semiconductor is increased so that the intrinsic

carrier concentration is doubled, then:
(a)The majority carrier density doubles
(b)The minority carrier density doubles
(c)Both majority and minority carrier densities double
(d)None of the above
Answer (c)Both majority and minority carrier densities double

10. Which one of the following properties of a liquid does not affect its rate of
evaporation?
A. Volume
B. surface area
C. temperature
D. boiling point
Answer A. Volume

11. A corked bottle full of water when frozen will break because
A. the bottle contracts on freezing
B. the volume of water decreases on freezing
C. the volume of water increases on freezing
D. glass is a bad conductor of heat
Answer C. the volume of water increases on freezing

12. Mercury boils at

A. 100o C
B. 357o C
C. 247o C
D. 189o C
Answer B. 357o C
13. Crystals having low melting points are in
A. ionic bond
B. Vander waal’s bond
C. metallic bond
D. covalent bond
Ans: C. metallic bond

14.The number of octahedral void(s) per atom present in a cubic close-packed

structure is
a. 2
b. 4
c. 1
d. 3
Ans: c. 1

15.A metal crystallizes with a face-cantered cubic lattice. The edge of the unit cell is
408 pm. The diameter of the metal atom is [CBSE AIPMT 2012]

a. 144 pm
b. 204 pm
c. 288 pm
d. 408 pm
ANs: c. 288 pm

16.AB crystallizes in a body centred cubic lattice with edge length 'a' equal to 387
pm. The distance between two oppositely charged ions in the lattice is
a. 300 pm
b. 335 pm
c. 250 pm
d. 200 pm
Ans: b 335 pm

17.Percentage of free space in a body centred cubic unit cell is

a. 34%
b. 28%
c. 20%
Ans: a 32%

18.If NaCl is doped with 10–4mol % of Sr Cl2, the concentration of cation vacancies
will be (NA = 6.02 × 1023mol–1)

a.6.02 × 1016mol–1
b.6.02 × 1017mol–1
c.6.02 × 1014mol–1
d.6.02 × 1015mol–1
ANS: b.6.02 × 1017mol–1

19.The appearance of colour in solid alkali metal halides is generally due to

a. Schottky defect
b. Frenkel defect
c. Interstitial position
d. F-centres
Ans: d F-centres

20.In a face-centered cubic lattice, a unit cell is shared equally by how many unit
cells?
a. 2
b. 4
c. 6
d. 8
Ans: c 6
21.A compound formed by elements X and Y crystallizes in a cubic structure in
which atoms X are at the corners of the cube and atoms Y are at the face-centers. The
formula of the compound is [CBSE AIPMT 2004]
a. X3Y
b. XY
c. XY2
d. XY3
Ans: d XY3

22.The pyknometric density of sodium chloride crystal is 2.165 ×103 kg m–3 while its
X-ray density is 2.178 × 103 kg m–3. The fraction of the unoccupied sites in sodium
chloride crystal is

a.5.96
b.5.96 × 10–2
c.5.96 × 10–1
d.5.96 × 10–3
Ans: d 5.96 × 10–3

23.In a compound, atoms of element Y form ccp lattice and those of element X
occupy 2/3rd of tetrahedral voids. The formula of the compound will be
a.X3Y4
b.X4Y3
c.X2Y3
d.X2Y
Ans: b.X4Y3

24.An ionic compound has a unit cell consisting of A ions at the corners of a cube
and B ions on the centres of faces of the cube. The empirical formula of the
compound would be
 a. AB
b. A2B
c. AB3
d. A3B
ANs: c AB3

25.How many unit cells are present in a cube-shaped ideal crystal of NaCl of mass
1.0 g?
a.5.14 × 1021 unit cells
b.1.28 × 1021 unit cells
c.1.71 × 1021 unit cells
d.2.57 × 1021 unit cells
Ans: d 2.57 × 1021 unit cells

26.Which of the following is a molecular crystal?

a. Dry ice
b. Quartz
c. Rock salt
d. Diamond
Ans: a. Dry ice

27.The edge length of a face centred cubic cell of an ionic substance is 508 pm. If the
radius of the cation is 110 pm, the radius of the anion is
a. 288 pm
b. 144 pm
c. 618 pm
d. 398 pm
Ans: b.144 pm

28.Sodium chloride, NaCl usually crystallizes in a face centred cubic lattice. How
many ions are in contact with any single Na+ ion?
a. 8
b. 6
c. 4
d. 1
Ans: b. 6

29.Percentage of free space in cubic close packed structure and in body centred
packed structure are respectively
a. 30% and 26%
b. 48% and 26%
c. 32% and 48%
d. 26% and 32%
 Ans: d. 26% and 32%

30.The packing efficiency of the two dimensional square unit cell shown is

a. 39.27%
b. 68.02%
c. 74.05%
d. 78.54%
Ans: d 78.54%

31.AB crystallizes in a body centred cubic lattice with edge length 'a' equal to 387
pm. The distance between two oppositely charged ions in the lattice is
a. 200 pm
b. 300 pm
c. 335 pm
d. 250 pm
Ans: c. 335 pm

32.A compound contains two types of atoms X and Y. It crystallizes in a cubic lattice
with atoms X at the corners of the unit cell and atoms Y at the body centre. The
simplest possible formula of this compound is:
a. X8Y
b. X2Y
c. XY
d. XY8
Ans: c. XY

33.A compound of 'A' and 'B' crystallizes in a cubic lattice in which the 'A' atoms
occupy the lattice points at the corners of the cube. The 'B' atoms occupy the centre
of each face of the cube. The probable empirical formula of the compound is
a. AB3
b. AB
c. A3B
d. AB2
Ans: a. AB3
34.Lithium metal crystallises in a body centred cubic crystal. If the length of the side
of the unit cell of lithium is 351 pm, the atomic radius of the lithium will be:
a.300.5 pm
b.75.5 pm
c.151.8 pm
d.240.8 pm
ANs: c 151.8 pm
35.Copper crystallises in a face-centred cubic lattice with a unit cell length of 361
pm. What is the radius of copper atom in pm?
a.108
b.181
c.157
d.128
Ans: d. 128

36.Copper crystallizes in fcc with a unit cell length of 361 pm. What is the radius of
copper atom?

a.157 pm
b.127 pm
c.108 pm
d.181 pm
ANs: b 127 pm

37.A compound is formed by elements A and B. This crystallizes in the cubic

structure where A atoms are at the corners of the cube and B atoms are at the body
centres. The simplest formula of the compound is
a. AB
b. AB6
c. A6B
d. A8B4
Ans a. AB

38.An ionic compound is expected to have tetrahedral structure if r+/r- lies in the
range of
a.0.414 to 0.732
b.0.732 to 1
c.0.155 to 0.225
d.0.225 to 0.414
Ans: d. 0.225 to 0.414

39.In which of the following crystals alternate tetrahedral voids are occupied?
a.NaCl
b.ZnS
c.CaF2
d.Na2O
Ans: b. ZnS

40. Iron has a Body-Cantered Cubic (BCC) structure with atomic radius 0.123 Å.
Find the lattice constant.
A) 0
B) 4.587 Å
C) 2.314 Å
D) 0.2840 Å
Answer D 0.2840 Å

41. The interplanar spacing of (220) planes of a Face-centeredcubic( FCC) structure

is 1.7458 Å. Calculate the lattice constant.
A) 4.983 Å
B) 2.458 Å
C) 0
D) 5.125 Å
Answer A 4.983 Å

42. What is the lattice constant for FCC crystal having atomic radius 1.476 Å
A) 1.476 Å
B) 4.1748 Å
C) 5.216 Å
D) 0
Answer A 1.476 Å

43. What is the possible number of different types of lattices (3D)?

A) 4
B) 8
C) 14
D) 17
Answer C. 14

44. Why are the glasses of building milky?

A) it changes in properties
B) it becomes old
C) it is brittle
D) of unwanted deposits
Answer A. it changes in properties
45. Which of the following is a crystalline solid?
A) Isotropic substances
B) Anisotropic substances
C) Supercooled liquids
D) Amorphous solids
Answer B. Anisotropic substances

46. Which of the following covalent compounds conduct electricity?

A) Silica
B) Hydrogen chloride
C) Diamond
D) Graphite
Answer D. Graphite

47. When do ionic compounds conduct electricity?

A) When dissolved in water
B) In solid state
C) In gaseous state
D) They never conduct
Answer A. When dissolved in water

48. Which one of the following is the property of an ionic compound?

A) High melting and boiling points
B) Low melting and boiling points
C) Weak inter-atomic forces
D) Non-conductors of electricity
Answer A. High melting and boiling points

49. What will happen to the elastic property of Gold when Potassium is added to
gold?
A) The elastic property of gold decreases
B) The elastic property of gold remains unaltered
C) The elastic property of gold increases
D) Gold loses its elastic property
Answer C. The elastic property of gold increases

50. What is the effect of annealing (to remove hardness) on elasticity of materials?
A) Increases the elasticity
B) Decreases the elasticity
C) Has no effect on elasticity
D) Distorts the material
Answer B. Decreases the elasticity

51. When too many people stand on a bridge it collapses, why?

A) Due to increase in stress
B) Due to overweight
C) Due to improper construction
D) Due to friction
Answer A. Due to increase in stress

52.When a P-type and N-type semiconductors are joined together to form a PN

junction, what happens to the Fermi energy levels
(A)Fermi energy level decreases for N-type while increases for P-type until
equilibrium is obtained
(B)Fermi energy level increases for N-type while decreases for P-type until
equilibrium is obtained
(C)Fermi energy level remains constant but the distribution of holes and electrons
changes
(D)Fermi energy level remains unchanged and equilibrium is obtained
Answer : A. Fermi energy level decreases for N-type while increases for P-type
until equilibrium is obtained

53.What happens to the Fermi energy level if a forward bias is applied to a PN

junction diode?
(A)Fermi energy level decreases for N-type while increases for P-type
(B)Fermi energy level increases for N-type while decreases for P-type
(C)Fermi energy levels remains in equilibrium in both regions to allow current to
flow
(D)Fermi energy levels increases for both the regions
Answer: B. Fermi energy level increases for N-type while decreases for P-type

54.What happens to the Fermi energy level if a reverse bias is applied to a PN

junction diode?
(A)Fermi energy level decreases for N-type while increases for P-type
(B)Fermi energy level increases for N-type while decreases for P-type
(C)Fermi energy levels remains in equilibrium in both regions to allow current to
flow
(D)Fermi energy levels increases for both the regions
Answer: A. Fermi energy level decreases for N-type while increases for P-type

55.When a P-type and N-type semiconductors are joined to form a PN junction

(A)The electrons are transferred from P-region to N-region and Fermi energy level of
both regions decreases
(B)The electrons are transferred from P-region to N-region and Fermi energy level of
both regions increases
(C)The electrons are transferred from N-region to P-region and Fermi energy level
both regions attain equilibrium
(D)The electrons are transferred from N-region to P-region and Fermi energy level of
both regions increases
Answer Ans: C. The electrons are transferred from N-region to P-region and
Fermi energy level both regions attain equilibrium

56.In equilibrium state of a PN junction diode

(A)Fermi energy level of P-region is higher than that of N-region
(B)Fermi energy level of N-region is lower than that of P-region
(C)Fermi energy levels of both the regions are at minimum value
(D)Fermi energy levels of both the regions attend thermal equilibrium
Answer: D Fermi energy levels of both the regions attend thermal equilibrium

57.In an equilibrium state of an NPN transistor, what is true for Fermi energy levels
(A)(Fermi energy emitter) > (Fermi energy base) > (Fermi energy collector)
(B)(Fermi energy emitter) < (Fermi energy base) > (Fermi energy collector)
(C)(Fermi energy emitter) = (Fermi energy base) = (Fermi energy collector)
(D)(Fermi energy emitter) > (Fermi energy base) < (Fermi energy collector)
Answer : C.(Fermi energy emitter) = (Fermi energy base) = (Fermi energy
collector)

58.For a biased NPN transistor, what is true for Fermi energy levels.
(A)(Fermi energy emitter) > (Fermi energy base) > (Fermi energy collector)
(B)(Fermi energy emitter) < (Fermi energy base) > (Fermi energy collector)
(C)(Fermi energy emitter) = (Fermi energy base) = (Fermi energy collector)
(D)(Fermi energy emitter) > (Fermi energy base) < (Fermi energy collector)
Answer: A. (Fermi energy emitter) > (Fermi energy base) > (Fermi energy
collector)

59.Hall effect is true for

(A)Metals only
(B)Semiconductors only
(C)Both metals and semiconductors
(D)For N-type semiconductors only
Answer: C. Both metals and semiconductors

60.Hall effect is true for

(A)Both N-type and P-type semiconductors
(B)N-type Semiconductors only
(C)P-type Semiconductors only
(D)Metals only
Answer A. Both N-type and P-type semiconductors

61.When current flows along the length of the semiconductor slab and magnetic field
applied is perpendicular the length to Hall voltage developed is
(a)Along the length
(b)Along the thickness
(c)Along the width
(d)Along the edges from where current enters
Ans: C. Along the width

62.In Hall effect, if only the direction of the current is changed in the material
(a)The value of Hall voltage developed increases
(b)The value of Hall voltage developed in opposite direction, but its value remains
constant
(c)The value of Hall voltage developed decreases
(d)The Hall effect do not appear
Ans: B. The value of Hall voltage developed in opposite direction, but its value
remains constant

63.In Hall effect, if only the direction of the magnetic field applied to the material is
changed
(a)The value of Hall voltage appears.
(b)The value of Hall voltage developed decreases.
(c)The value ofHall voltage developed in opposite direction, but its value remains
constant.
(d)The Hall effect do not appear.
Ans: C. The value ofHall voltage developed in opposite direction, but its value
remains constant.

64.In Hall effect, if only the direction of the current is changed in the material the
Hall electric field
(A)Hall electric field is developed in opposite direction
(B)Hall electric field do not change the direction
(C)Hall electric field increases
(D)Hall electric field decreases
Ans: A. Hall electric field is developed in opposite direction

65.If the thickness of the material is reduced, the Hall voltage developed
(a)Decreases
(b)Increases
(c)Remains constant
(d)Changes the direction
Ans: B. Increases
66.If the thickness of the material is increased, the Hall voltage developed
(a)Decreases
(b)Increases
(c)Remains constant
(d)Changes the direction
Ans: A. Decreases

67.If the strength of magnetic field is increased, the Hall voltage developed
(a)Decreases
(b)Remains constant
(c)Increases
(d)Changes the direction
Ans: C. Increases

68.If the strength of magnetic field is decreased, the Hall voltage developed
(a)Decreases
(b)Increases
(c)Remains constant
(d)Changes the direction
Ans: A. Decreases

69.If the magnitude of current is increased, the Hall voltage developed

(a)Decreases
(b)Increases
(c)Remains constant
(d)Changes the direction
Ans: B. Increases

70. If the magnitude of current is decreased, the Hall voltage developed

(a)Decreases
(b)Increases
(c)Remains constant
(d)Changes the direction
Ans: A. Decreases

71.If the density of charge carriers is increased, the value of Hall voltage
(a)Decreases
(b)Increases
(c)Remains constant
(d)Changes the direction
Ans: A. Decreases

72.Which of the following statements correctly describes a metalwithin band theory?

(a)A material possessing moderate band gap
(b)A material possesses a large band gap
(c)A material with zero band gap
(d)A material with infinite band gap
Ans:C. A material with zero band gap

73.Which is the correct ordering of the band gaps energy?

(a)Diamond > silicon > copper
(b)Diamond < silicon < copper
(c)Diamond < silicon > copper
(d)Diamond < silicon < copper
Ans: A. Diamond > silicon > copper

74.Which statement is true regarding electrical conductivity of materials?

(a)Electrical conductivity of a metal increases with temperature
(b)Electrical conductivity of a semiconductor increases with temperature
(c)Electrical conductivity of a metal decreases with temperature
(d)Electrical conductivity of a semiconductor decreases with temperature
Ans:B. Electrical conductivity of a semiconductor increases with temperature

75.Which statement is incorrect at ordinary room temperature?

(a)In metals electron can jump from valence band to conduction band easily
(b)In semiconductors few electrons can jump from valence band to conduction band
(c)In semiconductors is pure insulator at ordinary room temperature
(d)In insulators electrons cannot jump from valence band to conduction band
Ans C. In semiconductors is pure insulator at ordinary room temperature

76.Which statement is incorrect about semiconductors?

(a)A charge carrier may be either a positive hole or an electron
(b)Ga-doped Si is a p-type semiconductor
(c)n-and p-type semiconductors are intrinsic semiconductors
(d)Doping Si with As introduces a donor level below the conduction band
Ans C. n-and p-type semiconductors are intrinsic semiconductors

77.At 0 Kelvin, semiconductors are

(a)Perfect metals
(b)Perfect semiconductors
(c)Perfect non-metals
(d)Perfect insulator
Ans D. Perfect insulator

78Solids with high value of conductivity are called:

(a)Conductors
(b)Non-metal
(c)Insulator
(d)Semi-conductor
Ans A. Conductors

79.The electrons in valence band are

(a)Freely moving inside the solid
(b)Tightly bonded inside the solid
(c)Lies in the innermost orbits and cannot be made free
(d)Lies in the outermost orbits and cannot be made free
Ans A. Freely moving inside the solid

80.For metals conduction band and valence band are

(a)Fully occupied
(b)Empty
(c)Partially occupied
(d)Overlapping
Ans D. Overlapping

81.For a metal which is the incorrect statement?

(a)Electrons are freely moving in the solid and have energy greater than valence
electrons
(b)Electrons can remain simultaneously in conduction band and valence band
(c)Electrons in valence band may have energy equal to conduction band
(d)Electrons in valence band cannot have energy equal to conduction band
Ans D. Electrons in valence band cannot have energy equal to conduction band

82.What is the correct statement for an insulator?

(a)The band gap energy is very high
(b)The conduction band and valence cannot overlap
(c)The conduction band and valence band may overlap
(d)The conduction band and valence cannot have very little difference of energy
Ans B. The conduction band and valence cannot overlap

83.Pure silicon at 0 K is an
(a)Intrinsic semiconductor
(b)Extrinsic semiconductor.
(c)Metal
(d)Insulator
Ans D. Insulator

84.The energy required to break a covalent bond in a semiconductor

(a)is equal to 1 eV
(b)is equal to the width of the forbidden gap
(c)is greater in Ge than in Si
(d)is the same in Ge and Si
Ans B. is equal to the width of the forbidden gap

85.As electrons in conduction band have high energy, where is their location in
solids?
(a)Always near the top of the crystal
(b)Always at the surface of the crystal
(c)Anywhere in the solid moving freely
(d)Always bound to its parent atomic outermost orbit
Ans C. Anywhere in the solid moving freely

86.At 0 K, all the valence electrons in an intrinsic semiconductor

(a)are in the valence band
(b)are in the forbidden gap
(c)are in the conduction band
(d)are free electrons
Ans A. are in the valence band

87.P-type and N-type extrinsic semiconductors are formed by adding impurities of

valency?
(a)5 and 3 respectively.
(b)5 and 4 respectively.
(c)3 and 5 respectively.
(d)3 and 4 respectively.
Ans C. 3 and 5 respectively.

88.In an insulator, the forbidden energy gap is of the order of

(a)1 MeV
(b)0.1 MeV
(c) eV
(d) 5eV
Ans D. 5eV
89.At 0 K temperature, a p-type semiconductor
(a)Does not have any charge carriers
(b)Has few electrons and few free holes
(c)Has few holes but no electrons
(d)Has equal number of holes and electrons
Ans A. Does not have any charge carriers

90.The bond that exists in a semiconductor is

(a)Ionic bond
(b)Covalent bond
(c)Metallic bond
(d)Hydrogen bond
Ans B. Covalent bond

91A pure semiconductor behaves slightly as a conductor at

(a)Only at very high temperatures
(b)Only above room temperature
(c)At any energy above 0 K
(d)Only at room temperature
Ans C. At any energy above 0 K

92.Fermi level for a metal is

(a)Highest energy level occupied by electrons at 0 0C
(b)Average value of all available energy levels
(c)Highest energy level occupied by electrons at 0 K
(d )Addition of energy of all available electron energy levels
Ans A. Highest energy level occupied by electrons at 0 0C

93.Fermi level for an intrinsic semiconductor is

(a)Highest energy level occupied by electrons at 0 0C
(b)Average value of all available energy levels
(c)Highest energy level occupied by electrons at 0 K
(d)Reference energy level at the centre of the forbidden energy gap
Ans D.Reference energy level at the centre of the forbidden energy gap

94.What is the position of Fermi level in an n-type semiconductor?

(a)In between energy levels of conduction band and donor atoms
(b)In between energy levels of donor atoms and Fermi energy levels
(c)In between energy levels of valence band and Fermi level
(d)Close to the valence band
Ans B. In between energy levels of donor atoms and Fermi energy levels

95.The Fermi Function represents the probability of occupation which of the

following energy level by an electron?
(a)For electrons only at Fermi energy level
(b)For electrons at any energy level
(c)For electrons only above Fermi energy level
(d)For electrons only below Fermi energy level
Ans B. For electrons at any energy level

96Fermi level represents the energy level with probability of its occupation of
(a)0 %
(b)25 %
(c)50 %
(d)100 %
Ans C. 50 %

97.The probability of occupancy of electrons above Fermi level at T=0°K is

(a)0 %
(b)25%
(c)50%
(d)100%
Ans A. 0 %

98.The probability of occupancy of electrons below Fermi level at T=0°K is

(a)0 %
(b)25%
(c)50%
(d)100%
Ans D 100%

99.The energy level of a donor atom typically lies very close to

(a)Just above the conduction band
(b)just below the conduction band
(c)just above the valence band
(d)just below the valence band
Ans B. just below the conduction band

100.The energy level of a acceptor atom typically lies very close to

(a)just above the conduction band
(b)just below the conduction band
(c)just above the valence band
(d)just below the valence band
Ans C just above the valence band
53Due to the addition of a donor atom the original Fermi energy level in an intrinsic
semiconductor
(a)moves toward conduction band
(b)moves toward valence band
(c)remains at the centre of the forbidden energy gap
(d)is not affected
A

54Due to the addition of an acceptor atom the original Fermi energy level in an
intrinsic semiconductor
(a)moves toward conduction band
(b)moves toward valence band
(c)remains at the centre of the forbidden energy gap
(d)is not affected

55The free electron theory could not explain which of the following properties?
(a) Electrical and thermal conductivity of metals
(b)Thermal and thermal conductivity of non-metal
(c)Ferromagnetism
(d)Ohm’s law
C

56Free electron theory is based on which of the following assumption?

(a)Electrons are freely moving only at the centre of the solid
(b)Electrons behaves are freely moving through entire the solid
(c)Electrons can move freely only at the top surface of the solid
(d)Electrons can move freely only along the surfaces of the solid
B

57Which statement is correct regarding the influence of temperature on

conductivity?
(a)Conductivity of metals increases with increase in temperature
(b)Conductivity of metals decreases with increase in temperature
(c)Conductivity of semiconductors decreases with increase in temperature
(d)Conductivity of semiconductors do not change with increase in temperature
B
58When light incidents on metals what is the effect on its conductivity?
(a)Conductivity almost remain constant with only little heating
(b)Conductivity increases along with little heating of the material
(c)Conductivity decreases along with little heating of the material
(d)Conductivity decreases as electrons are emitted from the material
A

59When light incidents on semiconductors, whatis the effect on its conductivity?

(a)Conductivity almost remain constant with little heating
(b)Conductivity is not affected
(c)Conductivity increases as electrons are promoted to conduction band after
absorbing light
(d)Conductivity decreases as electrons absorb photons and move with more random
motion
D

60What is the effect of impurity on metals?

(a)Impurity increases into increase of mobility of electrons
(b)Impurity result into more scattering of electrons and conductivity decreases
(c)Impurity result into more scattering of electrons and conductivity increases
(d)Impurity does not affect the conductivity
B

61Density of states function implies

(a)Number of available energy levels of electrons in unit volume per unit
temperature
(b)Number of available energy levels of electrons in unit volume
(c)Number of available energy levels of electrons in unit volume per unit energy
interval
(d)Number of available electrons of per unit volume of the solid
C

62Under the influence of external electric or magnetic field, when an electron moves
inside a solid what happens to its mass?
(a)The mass of electron is a constant quantity and it remains constant
(b)The mass of electron increases due to absorption of external energy
(c)The mass of electron increases or decreases depending on the potential of positive
ions
(d)The external field will only change the resistance, but mass of electron is not
affected
C

63What is the effect of at very high temperature on N-type semiconductors?

(a)Concentration of electrons and holes is almost equal due to ionization of donor
ions and it turns into intrinsic semiconductor
(b)Concentration of electrons is more and it becomes more negative
(c)More holes are created as electrons become free and it turns into P-type
semiconductor
(d)It turns more negative as more electrons will break the bonds and become free
A

64What is the effect of at very high temperature on P-type semiconductors?

(a)Concentration of electrons and holes is almost equal due to ionization of donor
ions and it turns into intrinsic semiconductor
(b)Concentration of holes is more and it becomes more positive
(c)More electrons are created and it turns into N-type semiconductor
(d)It turns more positive as more electrons will break the bonds and more holes are
created
A

65What is the effect of very high temperature on N-type semiconductors?

(a)Fermi level continue to increases as more electrons are free and conducting
(b)Fermi level continue to decreases as more electrons are free creating more holes
(c)Fermi level becomes equal to its intrinsic Fermi level is concentration of holes and
electrons is balanced
(d)Fermi level is unbalanced and fluctuates rapidly
C

67If the doping concentration of donor ions increased, what is the effect on Fermi
energy of N-type semiconductor?
(a)Fermi level increase but always remain below the energy level of conduction band
(b)Fermi level increases and merge into energy level of conduction band
(c)Fermi level increase and goes above the energy level of conduction band
(d)Fermi level is unbalanced and fluctuates rapidly
B

68If the doping concentration of acceptor ions increased, what is the effect on Fermi
energy of P-type semiconductor?
(a)Fermi level decreases but always remain above the energy level of valence band
(b)Fermi level decreases and merge into energy level of valence band
(c)Fermi level decreases increase and goes down the energy level of valence band
(d)Fermi level is unbalanced and fluctuates rapidly
B

69What is true regarding drift current?

(a)Drift current is caused because of unequal concentration of electrons within the
solid
(b)Drift current is caused because of unequal concentration of holes within the solid
(c)Drift current is caused due to smooth flow of electrons within the solid
(d)Drift current is caused because of random motion of electrons with ions or
electrons
D

70What is true regarding diffusion?

(a)Diffusion is caused because of random movement of electrons and holes within
the solid
(b)Diffusion is caused due removal of electrons in solid when power supply is
connected
(c)Diffusion is passing of electrons and holes through potential barrier
(d)Diffusion is caused because of unbalanced distribution of concentration of
electrons or holes within the solid
D

71If the density of charge carriers is increased, the value of Hall coefficient
(a)Decreases
(b)Increases
(c)Remains constant
(d)Changes the direction
A

72If the current flowing through the semiconductor slab along its length, Hall
voltage and electric field developed is due to accumulation of charge carriers
(a)Along opposite edges of its thickness
(b)Along opposite edges of its width
(c)Along opposite edgesof its length
(d)Along the ends from where current enters
B

73For silicon doped with trivalent impurity,

(a)ne>>nh
(b)ne >nh
(c)nh>> ne
(d)nh> ne
C

74The Fermi level in an n-type semiconductor at 00K lies

(a)Below the donor level.
(b)Half way between the bottom of conduction band and donor level.
(c)Exactly in the middle of hand gap.
(d)Half way between the top of valence band and the acceptor level.
B

75If the Fermi energy of silver at 00K is 5 electron volt, the mean energy of electron
in silver at 00K is
(a)6 electron volt.
(b)12 electron volt.
(c)1.5 electron volt.
(d)3 electron volt.
D

76The probability of occupation of an energy level E, when E –EF = kT, is given by

(a)0.73
(b)0.63
(c)0.5
(d)0.27
D

77Which of the following elements is a covalently bonded crystal?

(a)aluminium
(b)sodium chloride
(c)germanium
(d)lead
C

79Mobility of electron is
(a)Average flow of electrons per unit field.
(b)Average applied field per unit drift velocity.
(c)Average drift velocity per unit field.
(d)Reciprocal of conductivity per unit charge.
C

80Fermi level represents the energy level with probability of its occupation of
(a)0 %.
(b)25 %.
c)50 %.
(d)100 %.
C
81Hall effect can be used to measure
(a)mobility of semiconductors.
(b)conductivity of semiconductors.
(c)resistivityof semiconductors.
(d)all of these
D

82The energy required to break a covalent bond in a semiconductor

(a)is equal to 1 eV
(b)is equal to the width of the forbidden gap
(c)is greater in Ge than in Si
(d)is the same in Ge and Si
B

83At absolute zero temperature, the probability of finding an electron at an energy

level E is zero when(a)E < EF(b)E >Ef(c)2E E = f (d)NoneB84Electrical
conductivity of insulators is in the range of _______.
(a)10-10(Ω-mm)-1
(b)10-10(Ω-cm)-1
(c)10-10(Ω-m)-1
(d)10-8(Ω-m)-1
A

85Units for electric field strength

(a)A/cm2
(b)mho/meter
(c)cm2/V.s
(d)V/cm
C

86Energy band gap size for semiconductors is in the range ________ eV.
(a)1-2
(b)2-3
(c)3-4
(d)> 4
B

87Energy band gap size for insulators is in the range ________ eV.
(a)1-2
(b)2-3
(c)3-4
(d)> 4
D

88Flow of electrons is affected by the following

(a)Thermal vibrations
(b)Impurity atoms
(c)Crystal defects
(d)all
D

89Flow of electrons is affected by the following

(a)Thermal vibrations
(b)Impurity atoms
(c)Crystal defects
(d)All

90Fermi energy level for p-type extrinsic semiconductors lies

(a)At middle of the band gap
(b)Close to conduction band
(c)Close to valence band
(d)None
B

91Fermi energy level for n-type extrinsic semiconductors lies

(a)At middle of the band gap
(b)Close to conduction band
(c)Close to valence band
(d)None
B

92Fermi energy level for intrinsic semiconductors lies

(a)At middle of the band gap
(b)Close to conduction band
(c)Close to valence band
(d)None
C

93Not an example for intrinsic semiconductor

(a)Si
(b)Al
(c)Ge
(d)Sn
A

94In intrinsic semiconductors, number of electrons __________ number of holes.

(a)Equal
(b)Greater than
(c)Less than
(d)Can not define
C

95In p-type semiconductors, number of holes __________ number of electrons.

(a)Equal
(b)Greater than
(c)Less than
(d)Twice
A

96Mobility of holes is ___________ mobility of electrons in intrinsic

semiconductors.
(a)Equal
(b)Greater than
(c)Less than
(d)Cannot define
D

97Fermi level for extrinsic semiconductor depends on

(a)Donor element
(b)Impurity concentration
(c)Temperature
(d)All
D

98To measure light intensity we use

(a)LED with forward bias
(b)LED with reverse bias
(c)photodiode with reverse bias
(d)photodiode with forward bias
C

99In integrated circuits, npn construction is preferred to pnpconstruction because

(a)npn construction is cheaper
(b)to reduce diffusion constant, n-type collector is preferred
(c)npn construction permits higher packing of elements
(d)p-type base is preferred
B

100The photoelectric work function of a surface is 2.2 eV. The maximum kinetic
energy of photo electrons emitted when light of wave length 6200 A.U. is incident on
the surface is
(a)1.6 eV
(b)1.4 eV
(c)1.2 eV
(d)Photo electrons are not emitted
D

101A metallic surface is irradiated by monochromatic light of frequency ν1and

stopping potential is found to be V1. If light of frequency ν2irradiates the surface, the
stopping potential will be
(a) V1+ (h/e) (ν1+ ν2)
(b)V1+ (h/e) (ν2–ν1)
(c)V1+ (e/h) (ν2–ν1)
(d)V1-(h/e) (ν1+ ν2)
B

102The retarding potential required to stop the emission of photoelectrons when a

photosensitive material of work function 1.2 eVis irradiated with ultraviolet rays of
wave length 2000 A.U. is
(a)4V
(b)5V
(c)6V
(d)8V
B

103The photoelectric effect is __________.

a)a relativistic effect
(b)the production of current by silicon solar cells when exposed to sunlight
(c)the total reflection of light by metals giving them their typical lustre
(d)the ejection of electrons by a metal when struck by lightens
D

104Substances which allow electric current to pass through them are called
(a)Conductors
(b)insulation
(c)semi-conductors
(d)none of the above
A

105A copper wire of length l and diameter d has potential difference V applied at its
two ends. The drift velocity is vd. If the diameter of wire is made d/3, then drift
velocity becomes
(a)9 vd
(b)vd/ 9
(c)vd/3
(d)vd.
D

106The unit of electrical conductivity is

(a)mho / metre
(b)mho / sq. m
(c)ohm / metre
(d)ohm / sq. m.
A

107All good conductors have high

(a)resistance
(b)electrical conductivity
(c)electrical and thermal conductivity
(d)conductance.
D

108A silicon sample is uniformly doped with 1016phosphorus atoms/cm3and 2 ×

1016boron atoms/cm3. If all the dopants are fully ionized, the material is:
(a)n-type with carrier concentration of 3 × 1016/cm3
(b)p-type with carrier concentration of 1016/cm3A
(c)p-type with carrier concentration of 4 × 1016/cm3
(d)Intrinsic
B

109Measurement of Hall coefficient enables the determination of:

(a)Mobility of charge carriers
(b)Type of conductivity and concentration of charge carriers
(c)Temperature coefficient and thermal conductivity
(d)None of the above
B
110The probability that an electron in a metal occupies the Fermi-level, at any
temperature (>0 K) is:
(a)0
(b)1
(c)0.5
(d)None of these
C

111the conductivity of an intrinsic semiconductor is given by (symbols have the

usual meanings):
(a)σi= eni2(μn–μp)
(b)σi= eni(μn–μp)
(c)σi= eni(μn+ μp)
(d)none of the above
C

112The Hall coefficient of sample (A) of a semiconductor is measured at room

temperature. The Hall coefficient of (A) at room temperature is 4×10–4m3coulomb–
1. The carrier concentration in sample A at room temperature is:
(a)~ 1021m–3
(b)~ 1020m–3
(c)~ 1022m–3
(d)None of the above
C

113If the drift velocity of holes under a field gradient of 100v/m is 5m/s, the mobility
(in the same SI units) is
(a)0.05
(b)0.55
(c)500
(d)50
A

114The Hall Effect voltage in intrinsic silicon is:

(a)Positive
(b)Zero
(c)Negative
w3z(d)None of the above
C

115The Hall coefficient of an intrinsic semiconductor is:

(a)Positive under all conditions
(b)Negative under all conditions
(c)Zero under all conditions
(d)None of the above
B

116Consider the following statements: pure germanium and pure silicon are
examples of:
1. Direct band-gap semiconductors
2. Indirect band-gap semiconductors
3. Degenerate semiconductors
which of these statements are true?

(a)1 alone is correct

(b)2 alone is correct
(c)3 alone is correct
(d)None of the above
A

119If the temperature of an extrinsic semiconductor is increased so that the intrinsic

carrier concentration is doubled, then:
(a)The majority carrier density doubles
(b)The minority carrier density doubles
(c)Both majority and minority carrier densities double
(d)None of the above
C