Semiconductor Electronics- 1 Practice Questions - DPP for NEET

 Page 1


DIRECTIONS (Q.1-Q.21) : There are 21 multiple choice
questions. Each question has 4 choices (a), (b), (c) and (d), out
of which ONLY ONE choice is correct.
Q.1 When a semiconductor is heated, its resistance
(a) decreases (b) increases
(c) reamins unchanged (d) nothing is definite
Q.2 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
Q.3 The forbidden energy band gap in conductors,
semiconductors and insulators are EG
1
, EG
2
 and EG
3
respectively. The relation among them is
(a) EG
1
 = EG
2
 = EG
3
(b) EG
1
 < EG
2
 < EG
3
(c) EG
1
 > EG
2
 > EG
3
(d) EG
1
 < EG
2
 > EG
3
Q.4 Let n
h
 and n
e
 be the number of holes and conduction
electrons respectively in a semiconductor. Then
(a)n
h
 > n
e
in an intrinsic semiconductor
(b)n
h
 = n
e
in an extrinsic semiconductor
(c)n
h
 = n
e 
in an intrinsic semiconductor
(d)n
e
 > n
h 
in an intrinsic semiconductor
Q.5 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
Page 2


DIRECTIONS (Q.1-Q.21) : There are 21 multiple choice
questions. Each question has 4 choices (a), (b), (c) and (d), out
of which ONLY ONE choice is correct.
Q.1 When a semiconductor is heated, its resistance
(a) decreases (b) increases
(c) reamins unchanged (d) nothing is definite
Q.2 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
Q.3 The forbidden energy band gap in conductors,
semiconductors and insulators are EG
1
, EG
2
 and EG
3
respectively. The relation among them is
(a) EG
1
 = EG
2
 = EG
3
(b) EG
1
 < EG
2
 < EG
3
(c) EG
1
 > EG
2
 > EG
3
(d) EG
1
 < EG
2
 > EG
3
Q.4 Let n
h
 and n
e
 be the number of holes and conduction
electrons respectively in a semiconductor. Then
(a)n
h
 > n
e
in an intrinsic semiconductor
(b)n
h
 = n
e
in an extrinsic semiconductor
(c)n
h
 = n
e 
in an intrinsic semiconductor
(d)n
e
 > n
h 
in an intrinsic semiconductor
Q.5 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
2
DPP/ P 57
Q.6 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
Q.7 In extrinsic P and N-type, semiconductor materials, the
ratio of the impurity atoms to the pure semiconductor
atoms is about
(a)1 (b) 10
–1
(c) 10
–4
(d) 10
–7
Q.8 At zero Kelvin a piece of germanium
(a) becomes semiconductor
(b) becomes good conductor
(c) becomes bad conductor
(d) has maximum conductivity
Q.9 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 obtanied 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
Q.10 The intrinsic semiconductor becomes an insulator at
(a) 0°C (b) –100°C
(c) 300 K (d) 0 K
Q.11 Energy bands in solids are a consequence of
(a) Ohm’s Law
(b) Pauli’s exclusion principle
(c) Bohr’s theory
(d) Heisenberg’s uncertainty principle
Q.12 The energy gap for diamond is nearly
(a) 1 ev (b) 2 ev (c) 4 ev (d) 6 ev
Q.13 The valence band and conduction band of a solid overlap at
low temperature, the solid may be
(a) metal (b) semiconductor
(c) insulator (d) None of these
Q.14Choose the correct statement
(a) When  we heat a semiconductor its resistance
increases
(b) When  we heat a semiconductor its resistance
decreases
(c) When we cool a semiconductor to 0 K then it becomes
super conductor
(d) Resistance of a semiconductor is independent of
temperature
Q.15 If 
e
n and v
d 
be the number of electrons and drift velocity
in a semiconductor. When the temperature is increased
(a)n
e
 increases and v
d 
decreases
(b)n
e
 decreases and v
d 
increases
(c) Both n
e 
and v
d 
increases
(d) Both n
e 
and v
d 
decreases
Q.16 The reverse biasing in a PN junction diode
(a) decreases the potential barrier
(b) increases the potential barrier
(c) increases the number of minority charge carriers
(d) increases the number of majority charge carriers
Q.17 Two PN-junctions can be connected in series by three
different methods as shown in the figure. If the potential
difference in the junctions is the same, then the correct
connections will be
P P N P N P N N P N P N
+ + + – – –
1 2 3
(a) In the circuit (1) and (2)
(b) In the circuit (2) and (3)
(c) In the circuit (1) and (3)
(d) Only in the circuit (1)
Page 3


DIRECTIONS (Q.1-Q.21) : There are 21 multiple choice
questions. Each question has 4 choices (a), (b), (c) and (d), out
of which ONLY ONE choice is correct.
Q.1 When a semiconductor is heated, its resistance
(a) decreases (b) increases
(c) reamins unchanged (d) nothing is definite
Q.2 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
Q.3 The forbidden energy band gap in conductors,
semiconductors and insulators are EG
1
, EG
2
 and EG
3
respectively. The relation among them is
(a) EG
1
 = EG
2
 = EG
3
(b) EG
1
 < EG
2
 < EG
3
(c) EG
1
 > EG
2
 > EG
3
(d) EG
1
 < EG
2
 > EG
3
Q.4 Let n
h
 and n
e
 be the number of holes and conduction
electrons respectively in a semiconductor. Then
(a)n
h
 > n
e
in an intrinsic semiconductor
(b)n
h
 = n
e
in an extrinsic semiconductor
(c)n
h
 = n
e 
in an intrinsic semiconductor
(d)n
e
 > n
h 
in an intrinsic semiconductor
Q.5 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
2
DPP/ P 57
Q.6 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
Q.7 In extrinsic P and N-type, semiconductor materials, the
ratio of the impurity atoms to the pure semiconductor
atoms is about
(a)1 (b) 10
–1
(c) 10
–4
(d) 10
–7
Q.8 At zero Kelvin a piece of germanium
(a) becomes semiconductor
(b) becomes good conductor
(c) becomes bad conductor
(d) has maximum conductivity
Q.9 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 obtanied 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
Q.10 The intrinsic semiconductor becomes an insulator at
(a) 0°C (b) –100°C
(c) 300 K (d) 0 K
Q.11 Energy bands in solids are a consequence of
(a) Ohm’s Law
(b) Pauli’s exclusion principle
(c) Bohr’s theory
(d) Heisenberg’s uncertainty principle
Q.12 The energy gap for diamond is nearly
(a) 1 ev (b) 2 ev (c) 4 ev (d) 6 ev
Q.13 The valence band and conduction band of a solid overlap at
low temperature, the solid may be
(a) metal (b) semiconductor
(c) insulator (d) None of these
Q.14Choose the correct statement
(a) When  we heat a semiconductor its resistance
increases
(b) When  we heat a semiconductor its resistance
decreases
(c) When we cool a semiconductor to 0 K then it becomes
super conductor
(d) Resistance of a semiconductor is independent of
temperature
Q.15 If 
e
n and v
d 
be the number of electrons and drift velocity
in a semiconductor. When the temperature is increased
(a)n
e
 increases and v
d 
decreases
(b)n
e
 decreases and v
d 
increases
(c) Both n
e 
and v
d 
increases
(d) Both n
e 
and v
d 
decreases
Q.16 The reverse biasing in a PN junction diode
(a) decreases the potential barrier
(b) increases the potential barrier
(c) increases the number of minority charge carriers
(d) increases the number of majority charge carriers
Q.17 Two PN-junctions can be connected in series by three
different methods as shown in the figure. If the potential
difference in the junctions is the same, then the correct
connections will be
P P N P N P N N P N P N
+ + + – – –
1 2 3
(a) In the circuit (1) and (2)
(b) In the circuit (2) and (3)
(c) In the circuit (1) and (3)
(d) Only in the circuit (1)
DPP/ P 57
3
Q.18The approximate ratio of resistances in the forward and
reverse bias of the PN-junction diode is
(a) 10
2
 : 1 (b) 10
–2
 : 1
(c) 1 : 10
–4
(d) 1 : 10
4
Q.19The dominant mechanisms for motion of charge carriers
in forward and reverse biased silicon P-N junctions are
(a) Drift in forward bias, diffusion in reverse bias
(b) Diffusion in forward bias, drift in reverse bias
(c) Diffusion in both forward and reverse bias
(d) Drift in both forward and reverse bias
Q.20In a triclinic crystal system
(a) a ¹ b ¹ c, a ¹ b ¹ g
(b) a = b = c, a ¹ b ¹ g
(c) a ¹ b ¹ c, a ¹ b = g
(d) a = b = c, a = b = g
Q.21The correct cymbol for zener diode is
(a)
(b)
+ –
(c)
+ –
(d)
+
–
DIRECTIONS (Q.22-Q.24) : In the following questions,
more than one of the answers  given are correct. Select the
correct answers and mark it according to the following
codes:
Codes :
(a) 1, 2 and 3 are correct (b) 1 and 2 are correct
(c) 2 and 4 are correct (d) 1 and 3 are correct
Q.22 In the given figure, which of the diodes are forward biased?
(1)
+10V
+5V R
(2)
–5V
–12V
R
(3)
–10V
R
(4)
–10V
R
Q.23 Which of the following materials are crystalline?
(1) Copper (2) Sodium chloride
(3) Diamond (4) Wood
Q.24 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 wrong statements?
(1) Resistance of each increases
(2) Resistance of each decreases
(3) Resistance of copper increases while that of
germanium decreases
(4) Resistance of copper decreases while that of
germanium increases
DIRECTIONS (Q.25-Q.27) : Read the passage given below
and answer the questions that follows :
A student performs an experiment for drawing the static
characteristic curve of a triode valve in the laboratory. The
following data were obtained from the linear portion of the
curves:
Grid voltage V
g
 (volt) –2.0 –3.5 –2.0
Plate voltage V
p
 (volt) 180 180 120
Plate current I
P
 (mA) 15 7 10
Q.25 Calculate the plate resistance r
p
 of the triode valve?
(a) 0.12 × 10
4
 ohm (b) 1.2 × 10
4
 ohm
(c) 1.3 × 10
4
 ohm (d) 1.4 × 10
4
 ohm
Page 4


DIRECTIONS (Q.1-Q.21) : There are 21 multiple choice
questions. Each question has 4 choices (a), (b), (c) and (d), out
of which ONLY ONE choice is correct.
Q.1 When a semiconductor is heated, its resistance
(a) decreases (b) increases
(c) reamins unchanged (d) nothing is definite
Q.2 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
Q.3 The forbidden energy band gap in conductors,
semiconductors and insulators are EG
1
, EG
2
 and EG
3
respectively. The relation among them is
(a) EG
1
 = EG
2
 = EG
3
(b) EG
1
 < EG
2
 < EG
3
(c) EG
1
 > EG
2
 > EG
3
(d) EG
1
 < EG
2
 > EG
3
Q.4 Let n
h
 and n
e
 be the number of holes and conduction
electrons respectively in a semiconductor. Then
(a)n
h
 > n
e
in an intrinsic semiconductor
(b)n
h
 = n
e
in an extrinsic semiconductor
(c)n
h
 = n
e 
in an intrinsic semiconductor
(d)n
e
 > n
h 
in an intrinsic semiconductor
Q.5 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
2
DPP/ P 57
Q.6 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
Q.7 In extrinsic P and N-type, semiconductor materials, the
ratio of the impurity atoms to the pure semiconductor
atoms is about
(a)1 (b) 10
–1
(c) 10
–4
(d) 10
–7
Q.8 At zero Kelvin a piece of germanium
(a) becomes semiconductor
(b) becomes good conductor
(c) becomes bad conductor
(d) has maximum conductivity
Q.9 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 obtanied 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
Q.10 The intrinsic semiconductor becomes an insulator at
(a) 0°C (b) –100°C
(c) 300 K (d) 0 K
Q.11 Energy bands in solids are a consequence of
(a) Ohm’s Law
(b) Pauli’s exclusion principle
(c) Bohr’s theory
(d) Heisenberg’s uncertainty principle
Q.12 The energy gap for diamond is nearly
(a) 1 ev (b) 2 ev (c) 4 ev (d) 6 ev
Q.13 The valence band and conduction band of a solid overlap at
low temperature, the solid may be
(a) metal (b) semiconductor
(c) insulator (d) None of these
Q.14Choose the correct statement
(a) When  we heat a semiconductor its resistance
increases
(b) When  we heat a semiconductor its resistance
decreases
(c) When we cool a semiconductor to 0 K then it becomes
super conductor
(d) Resistance of a semiconductor is independent of
temperature
Q.15 If 
e
n and v
d 
be the number of electrons and drift velocity
in a semiconductor. When the temperature is increased
(a)n
e
 increases and v
d 
decreases
(b)n
e
 decreases and v
d 
increases
(c) Both n
e 
and v
d 
increases
(d) Both n
e 
and v
d 
decreases
Q.16 The reverse biasing in a PN junction diode
(a) decreases the potential barrier
(b) increases the potential barrier
(c) increases the number of minority charge carriers
(d) increases the number of majority charge carriers
Q.17 Two PN-junctions can be connected in series by three
different methods as shown in the figure. If the potential
difference in the junctions is the same, then the correct
connections will be
P P N P N P N N P N P N
+ + + – – –
1 2 3
(a) In the circuit (1) and (2)
(b) In the circuit (2) and (3)
(c) In the circuit (1) and (3)
(d) Only in the circuit (1)
DPP/ P 57
3
Q.18The approximate ratio of resistances in the forward and
reverse bias of the PN-junction diode is
(a) 10
2
 : 1 (b) 10
–2
 : 1
(c) 1 : 10
–4
(d) 1 : 10
4
Q.19The dominant mechanisms for motion of charge carriers
in forward and reverse biased silicon P-N junctions are
(a) Drift in forward bias, diffusion in reverse bias
(b) Diffusion in forward bias, drift in reverse bias
(c) Diffusion in both forward and reverse bias
(d) Drift in both forward and reverse bias
Q.20In a triclinic crystal system
(a) a ¹ b ¹ c, a ¹ b ¹ g
(b) a = b = c, a ¹ b ¹ g
(c) a ¹ b ¹ c, a ¹ b = g
(d) a = b = c, a = b = g
Q.21The correct cymbol for zener diode is
(a)
(b)
+ –
(c)
+ –
(d)
+
–
DIRECTIONS (Q.22-Q.24) : In the following questions,
more than one of the answers  given are correct. Select the
correct answers and mark it according to the following
codes:
Codes :
(a) 1, 2 and 3 are correct (b) 1 and 2 are correct
(c) 2 and 4 are correct (d) 1 and 3 are correct
Q.22 In the given figure, which of the diodes are forward biased?
(1)
+10V
+5V R
(2)
–5V
–12V
R
(3)
–10V
R
(4)
–10V
R
Q.23 Which of the following materials are crystalline?
(1) Copper (2) Sodium chloride
(3) Diamond (4) Wood
Q.24 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 wrong statements?
(1) Resistance of each increases
(2) Resistance of each decreases
(3) Resistance of copper increases while that of
germanium decreases
(4) Resistance of copper decreases while that of
germanium increases
DIRECTIONS (Q.25-Q.27) : Read the passage given below
and answer the questions that follows :
A student performs an experiment for drawing the static
characteristic curve of a triode valve in the laboratory. The
following data were obtained from the linear portion of the
curves:
Grid voltage V
g
 (volt) –2.0 –3.5 –2.0
Plate voltage V
p
 (volt) 180 180 120
Plate current I
P
 (mA) 15 7 10
Q.25 Calculate the plate resistance r
p
 of the triode valve?
(a) 0.12 × 10
4
 ohm (b) 1.2 × 10
4
 ohm
(c) 1.3 × 10
4
 ohm (d) 1.4 × 10
4
 ohm
4
DPP/ P 57
Q.26 Calculate the mutual conductance g
m
 of the triode valve?
(a) 5.33 × 10
–3
 ohm
–1
(b) 53.3 × 10
–3
 ohm
–1
(c) 4.32 × 10
–3
 ohm
–1
(d) 5.00 × 10
–3
 ohm
–1
Q.27 Calculate the amplification factor µ, of the triode valve?
(a) 64 (b) 52
(c) 54 (d) 62
DIRECTIONS (Q. 28-Q.30) : Each of these questions contains
two statements: Statement-1 (Assertion) and Statement-2
(Reason). Each of these questions has four alternative choices,
only one of which is the correct answer. You have to select the
correct choice.
(a) Statement-1 is True, Statement-2 is True; Statement-2 is a
correct explanation for  Statement-1.
(b) Statement-1 is True, Statement-2 is True; Statement-2 is
NOT a correct explanation for Statement-1.
(c) Statement -1 is False, Statement-2 is True.
(d) Statement -1 is True, Statement-2 is False.
Q.28 Statement-1 : The number of electrons in a P-type silicon
semiconductor is less than the number of electrons in a
pure silicon semiconductor at room temperature.
Statement-2: It is due to law of mass action.
Q.29 Statement-1 : The resistivity of a semiconductor decreases
with temperature.
Statement-2 : The atoms of a semiconductor vibrate with
larger amplitude at higher temperature there by increasing
its resistivity.
Q.30 Statement-1 : We can measure the potential barrier of a
PN junction by putting a sensitive voltmeter across its
terminals.
Statement-2 : The current through the PN junction is not
same in forward and reversed bias.