TECHGURU CLASSES for SSC-JE / RAILWAYS / ORDINANCE
Basic Electronics : CHAPTER - 1 Semiconductor Materials and Properties
Objective Problems
1.
Ions are–
8.
(a) Same as electrons
(a) Has lower energy than an electron in
the valence band
(b) Same as holes
(b) Has a higher energy than an electron
in the valence band
(c) Atoms with excess or deficient electrons
(d) Molecules with excess or deficient
electrons
2.
(c) Is always chargeless
(d) Has tendency to leave the atom.
Insultating materials have the function of–
(a) Conducting very large currents
9.
(b) Preventing an open circuit between the
voltage source and the load
(c) Preventing a short circuit between
conducting wires
3.
4.
5.
6.
10.
Adding pentavalent or trivalent impurities
to a pure semiconductor is called–
(a) Combination
(b) Recombination
(c) Doping
(d) Depleting
(d) Storing very high currents
The n-type semiconductor has an.......of free
electrons, and the p-type has an excess of......
Which of the following is a semiconductor ?
(a) holes, electrons
(b) shortage, holes
(a) Arsenic
(b) Gallium arsenide
(c) excess, electrons
(d) excess, holes
(c) Phosphorus
(d) Diamond
11.
Doped silicon is called–
Which of the following is a tetravalent ?
(a) Intrinsic semiconductor
(a) Calcium
(b) Quartz
(b) Doped semiconductor
(c) Germanium
(d) Diamond
(c) Active semiconductor
Which of the following is not a
semiconductor ?
(d) Extrinsic semiconductor
12.
(a) Silicon
(b) Diamond
At absolute zero, a pure semiconductor
behaves like an insulator because–
(c) Germanium
(d) Gallium Arsenide
(a) Forbidden energy gap is reduced
(b) Drift velocity of free electrons is very
small
Which of the following statement about the
valence electrons in germanium and silicon
is correct ?
(c) No free electrons are available for
current conduction
(a) Germanium has four valence electrons
and silicon has two valance electrons.
(b) Germanium has two valence electrons
and silicon has four valance electrons.
13.
(c) Both germanium as well as silicon have
two valence electrons each.
(d) Both germanium as well as silicon have
four valence electrons each.
7.
An electron in the conduction band–
Which of the following element belongs to
the same group of periodic table as that of
silicon and germanium ?
(a) Boron
(b) Carbon
(c) Sodium
(d) Phosphorus
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(d) Recombination of electrons and holes
is slow
Match the following –
Column A
Column B
(A) Conductor
(B)
(C)
(D)
(a)
(b)
(c)
(i) Doped
Semiconductor (ii) Acceptor atom
Hole
(iii) 4-valence electrons
Extrinsic
(iv) Valence electron
A–(iii), B–(iv), C–(i), D–(ii)
A–(iv), B–(i), C–(ii), D–(iii)
A–(iii), B–(i), C–(iv), D–(ii)
(d) A–(iv), B–(iii), C–(ii), D–(i)
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TECHGURU CLASSES for SSC-JE/RAILWAYS/ORDINANCE
Basic Electronics : CHAPTER - 1 Semiconductor Materials and Properties
14.
Which of the following represents materials
in increasing order of specific resistance ?
(a) Steel, Gold, Aluminium, Copper
(c) Always above the forbidden level
(d) Concentrate holes for the flow of current
22.
(b) Gold,. Aluminium, Copper, Steel
(c) Gold, Copper, Aluminium, Steel
(d) Copper, Gold, Aluminium, Steel
15.
16.
17.
23.
(b) Electrons as minority carriers and holes
as majority carriers
(c) Only electrons as carriers
(d) Only holes as carriers
A p-type semiconductor results when
(a) A trivalent impurity is added to an
intrinsic semiconductor
(b) A pentavalent impurity is added to an
intrinsic semiconductor
24.
(c) Either a trivalent or pentavalent
impurity is added to an intrinsic
semiconductor
(d) Any of the above
The forbidden energy gap in
semiconductors lies–
(a) Between the valence band and
conduction band
(b) Just above the conduction band
Which of the following is trivalent ?
(a) Boron
(b) Indium
(c) Aluminium
(d) All of the above
The forbidden energy gap for silicon is–
(a) 0.3 eV
(b) 0.72 eV
(c) 1.1 eV
(d) 1.73 eV
A semiconductor has–
(a) Zero temperature coefficient of
resistance
(b) Positive temperature coefficient of
resistance
18.
19.
20.
21.
(c) Negative temperature coefficient of
resistance
(d) None of the above
An electron will not contribute to electric
current when
(a) It strikes a positive ion
(b) It losses its charge
(c) It is at higher temperature
(d) It is a completely filled bond
The movement of a hole results from –
(a) The vacancy filled by a valence electron
from the neighbouring atom
(b) Excitation due to high temperature
(c) Change in number of protons in the
atom
(d) Non of the above
A donor impurity must have only–
(a) Two valence electrons
(b) Three valence electrons
(c) Four valence electrons
(d) Five valence elecrons
The conduction band is –
(a) The region of free electrons
(b) A range of energies corresponding to
the energies of the free electrons
A n-type semiconductor has –
(a) Electrons as majority carriers and holes
as minority carriers
25.
26.
(c) Just below the conduction band
(d) Either above or below the conduction
band
The merging of a free electrons and a hole
is known as–
(a) Recombination (b) Extrusion
(c) Absorption
(d) Adsorption
The forbidden energy gap for silicon is 1.1
eV and that for germanium is 0.72 eV.
Hence it can be conducded that–
(a) Intrinsic silicon is a much poorer
conductor than germanium at room
temperature
(b) Intrinsic germanium is a much poorer
conductor than germanium at room
temperature
(c) Silicon holes have higher mobility as
compared to germanium holes
(d) Germanium holes have higher mobility
as compared to silicon holes
AGRA ALLAHABAD PATNA
NEW DELHI LUCKNOW
NOIDA BHOPAL JAIPUR GORAKHPUR KANPUR
8860637779 9919526958 9793424360 9919751941 9534284412 8860637779 9838004479 9793424360 9838004494 9838004497
38
TECHGURU CLASSES for SSC-JE / RAILWAYS / ORDINANCE
Basic Electronics : CHAPTER - 1 Semiconductor Materials and Properties
27.
The forbidden energy gap for diamond is –
(a) 0.53 eV
(b) 0.73 eV
(c) 1.13 eV
(d) 5.3 eV
lies–
(a) Near valence band
(b) Near conduction band
28.
Fermi level of for an intrinsic semiconductor
lies –
(a) Near valence band
(b) Near conduction band
(c) Middle of valence and conduction band
(d) Can lies anywhere
Fermi level for an n-type semiconductor
(c) In valence band
(d) In conduction band
Fermi level for p-type semiconductor lies–
(a) Near valence band
(b) Near conduction band
(c) In valence band
29.
30.
(d) In conduction band
Hint & Answers
1. (c) 2. (c)
3. (b) As we know that, there are some elements
of IVth group shows the property of
semiconductor.Whereas some compound
elements also shows the property of
semiconductor.
4. (c) Germanium is a tetravalent because there
are four electrons in the outer most orbit.
5. (b) 6. (d)
7. (b)
8.
(b)
9. (c) A semiconductor material in a pure form
is known as intrinsic semiconductor. At
room temperature few electrons are
present in the conduction band, that are
not sufficient for conduction.So in order
to increase the conductivity of a
semiconductor material one method is
to be used that is called “Doping”.
Doping can be defined as;
10.
14.
18.
22.
(d)
(c)
(d)
(a)
23. (a)
27. (d)
“The process of introducing the
impurities in semiconductors in a
precisely controlled manner is called
doping”. There are two types of
impurities
 Trivalent impurities
Pentavalent impurities
11. (d)
12. (c)
13. (d)
15. (b)
16. (c)
17. (c)
19. (a)
20. (a)
21. (b)
A n-type semiconductor is to be formed
when a pentavalent impurity is added
in a pure semiconductor.
24. (a) 25. (a) 26. (a)
28. (c) 29. (b) 30. (a)
nnn
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