NCERT Solutions for class 12 Physics | Chapter 14 - Semiconductor Electronics

Questions
1 The manifestation of band structure in solids is due to
A Heisenberg uncertainty priniciple
B Pauli’s exclusion principle
C Bohr’s correspondence principle
D Boltzmann law

Answer:Pauli’s exclusion principle
2 At absolute zero, Si acts as a
A metal
B semiconductor
C insulator
D none of these

Answer:insulator

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3 If the energy of a photon of sodium light (A = 589 nm) equals the band gap of semiconductor, the minimum energy required to create hole electron pair
A 1.1 eV
B 2.1 eV
C 3.2 eV
D 1.5 eV

Answer:2.1 eV
4 In a half wave rectifier circuit operating from 50 Hz mains frequency, the fundamental frequency in the ripple would be
A 25 Hz
B 50 Hz
C 70.7 Hz
D 100 Hz

Answer:50 H
5 What happens during regulation action of a Zener diode?
A The current through the series resistance (Rs) changes.
B The resistance offered by the Zener changes.
C The Zener resistance is constant.
D Both (a) and (b)

Answer:Both (a) and (b)
6 In good conducrors of electricity the type of bonding that exist is
A Van der Walls
B covalent
C ionic
D metallic

Answer:metallic
7 Carbon, silicon and germanium have four valence electrons each. These are characterised by valence and conduction bands separated by energy band gap respectively equal to (E^)c, (Eg)Si and (Eg)Ge. Which of the following statements is true?
A (Eg)Si < (Eg)Ge < (Eg)C
B (Eg)C< (Eg)Ge < (Eg)Si
C (Eg)C < (Eg)Si < (Eg)Ge
D (Eg)C = (Eg)Si < (Eg)Ge

Answer:(Eg)C < (Eg)Si < (Eg)Ge
8 A zener diode is specified as having a breakdown voltage of 9.1 V, with a maximum power dissipation of 364 mW. What is the maximum current the diode can handle?
A 40 mA
B 60 mA
C 50 mA
D 45 mA

Answer:40 mA
9 If in a n-type semiconductor when all donor states are filled, then the net charge density in the donor states becomes
A 1
B > 1
C < 1, but not zero
D zero

Answer:> 1
10 The breakdown in a reverse biased p-n junction diode is more likely to occur due to
A large velocity of the minority charge carriers if the doping concentration is small
B large velocity of the minority charge carriers if the doping concentration is large
C strong electric field in a depletion region if the doping concentration is small
D none of these

Answer:large velocity of the minority charge carriers if the doping concentration is large
11 Region without free electrons and holes in a p-n junction is
A n-region
B p-region
C depletion region
D none of these

Answer:depletion region
12 The probability of electrons to be found in the conduction band of an intrinsic semiconductor of finite temperature
A increases exponentially with increasing band gaP
B decreases exponentially with increasing band gap
C decreases with increasing temperature.
D is independent of the temperature and band gap

Answer:decreases exponentially with increasing band gap
13 In the circuit shown if current for the diode is 20 μA, the potential difference across the diode is

class 12 physics chapter 14 semiconductor

A 2 V
B 4.5 V
C 4 V
D 2.5 V

Answer:4 V
14 Potential barrier developed in a junction diode opposes the flow of
A minority carrier in both regions only
B majority carriers only
C electrons in p region
D holes in p region

Answer:majority carriers only
15 In an n-type silicon, which of the following statements is true.
A Electrons are majority carriers and trivalent atoms are the dopants’
B Electrons are minority carriers and pentava- lent atoms are the dopants.
C Holes are minority carriers and pentavalent atoms are the dopants.
D Holes are majority carriers and trivalent atoms are the dopants.

Answer:Holes are minority carriers and pentavalent atoms are the dopants.
16 Which of the following statements is incorrect for the depletion region of a diode?
A There the mobile charges exist.
B Equal number of holes and electrons exist, making the region neutral.
C Recombination of holes and electrons has taken place.
D None of these

Answer:There the mobile charges exist.
17 If a small amount of antimony is added to germanium crystal
A its resistance is increased
B it becomes a p-type semiconductor
C there will be more free electrons than holes in the semiconductor,
D none of these.

Answer:there will be more free electrons than holes in the semiconductor,
18 The dominant mechanism for motion of charge carriers in forward and reverse biased silicon p-n junction 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

Answer:diffusion in forward bias, drift in reverse bias
19 In an unbiased p-n junction, holes diffuse from the p-region to n-region because
A free electrons in the n-region attract them
B they move across the junction by the potential difference
C hole concentration in p-region is more as compared to u-region.
D all of these

Answer:hole concentration in p-region is more as compared to u-region.
20 To obtain electrons as majority charge carriers in a semiconductors the impurity mixed is:
A monovalent
B divalent
C trivalent
D pentavalent

Answer:divalent

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