Latest Objective Questions On Engineering Materials
1.The conductivity of a conductor can be increased by
decreasing its temperature
increasing its temperature
decreasing its vibration
increasing its vibration
ANSWER : : decreasing its temperature
2.The co-ordination number of a simple cubic structure is
2
4
6
8
ANSWER : : 6
3.By increasing impurity content in the metal alloy the residual resistivity always
decreases
increases
remains constant
becomes temperature independent
ANSWER : : increases
4.On which of the following factors does the resistivity of a material depend ?
Resistance of the conductor
Area of the conductor section
Length of the conductor
All of the above
ANSWER : : All of the above
5.The value of critical field below the transition temperature will
increase
decrease
remain unchanged
any of the above
ANSWER : : increase
6.The metal having the lowest temperature coefficient of resistance is
gold
copper
aluminium
kanthal
ANSWER : : gold
7.A perfect conductor has
zero conductivity
unity conductivity
infinite conductivity
none of the above
ANSWER : : infinite conductivity
8.Mercury as an electric contact material is
a liquid
a metal
a metal liquid
a gas
ANSWER : s: c
9.Commonly used conducting materials are
copper
aluminium
both (a) and (b)
copper and silver
ANSWER : : both (a) and (b)
10.In a superconductor the value of critical density depends upon
magnetic field strength
temperature
either (a) or (b)
both (a) and (b)
ANSWER : : both (a) and (b)
11.The formula ____ determines the number of electrons that can be accommodated in any level.
2n2
4n2
2n3
4ns
ANSWER : : 2n2
12.At transition temperature the value of critical field is
zero
negative real value
positive real value
complex value
ANSWER : : zero
13.The transition temperature of mercury is
18.0�K
9.22�K
4.12�K
1.14’K
ANSWER : : 4.12�K
14.The kinetic energy of a bounded electron is
less than that of unbounded electron
greater than that of unbounded electron
equal to that of unbounded electron
infinite
ANSWER : : less than that of unbounded electron
15.The covalent bond is formed by
transfer of electrons between atoms
sharing of electrons between atoms
sharing of variable number of electrons by a variable number of atoms
none of the above
ANSWER : s: b
16.is a negatively charged particle present in an atom.
Proton
Neutron
Electron
None of the above
ANSWER : : Electron
17.An H.R.C. fuse is
a ceramic body having metal and caps
a wire of platinum
a heavy cross-section of copper or aluminium
a ceramic tube having carbon rod inside it
ANSWER : : a ceramic body having metal and caps
18.The superconductivity is due to
the crystal structure having no atomic vibration at 0�K
all electrons interact in the super-conducting state
the electrons jump into nucleus at 0�K
none of the above
ANSWER : : the crystal structure having no atomic vibration at 0�K
19.The structure sensitive property of a super conductor is
critical magnetic field
transition temperature
critical current density
none of the above
ANSWER : : critical current density
20.The tiny block formed by the arrangement of a small group of atoms is called the
unit cell
space lattice
either (a) or (b)
none of the above
ANSWER : : unit cell
21.Which of the following materials is preferred for transmitting electrical energy over long distance ?
Copper
Aluminium
Steel reinforced copper
Steel reinforced aluminium
ANSWER : : Steel reinforced aluminium
22.Superconductors are becoming popular for use in
generating very strong magnetic field
manufacture of bubble memories
generating electrostatic field
generating regions free from magnetic field
ANSWER : : generating very strong magnetic field
23.The conductors have transport phenomena of electrons due to
electric field
magnetic field
electromagnetic field
none of the above
ANSWER : : electric field
24.Which of the following resistive materials has the lowest temperature co-efficient of resistance ?
Nichrome
Constantan
Kanthal
Molybdenum
ANSWER : : Nichrome
25.Superconductivity is observed for
infrared frequencies
d.c. and low frequency
a.c. and high frequency
frequencies having no effect
ANSWER : : d.c. and low frequency
26.The coils of D.C. motor starter are wound with wire of
copper
kanthal
manganin
nichrome
ANSWER : : manganin
27.Most of the common metals have _____ structure.
linear
hexagonal
orthorhombic
cubic
ANSWER : : cubic
28.A carbon resistor contains
carbon crystals
solid carbon granules
pulverized coal
finely divided carbon black.
ANSWER : : finely divided carbon black.
29._____ is a hard solder.
Tin-lead
Tin-silver-lead
Copper-zinc
None of the above
ANSWER : : Copper-zinc
30.Carbon electrodes are not used in
GLS lamps
electric arc furnace
dry cells
cinema projectors
ANSWER : : GLS lamps
31.Which of the following is the poorest conductor of electricity ?
Carbon
Steel
Silver
Aluminium
ANSWER : : Carbon
32.Constantan contains
silver and tin
copper and tungsten
tungsten and silver
copper and nickel
ANSWER : : copper and nickel
33._____ is the main constituent of glass
Fe203
Si02
AI2O3
B2O3
ANSWER : : Si02
34.Addition of 0.3 to 4.5% silicon to iron _____ the electrical resistivity of iron.
increases
decreases
does not change
increases
ANSWER : uper conductivity can be destroyed by
35.Total number of crystal systems is
2
4
7
12
ANSWER : : 7
36.Which of the following materials does not have covalent bonds ?
Organic polymers
Silicon
Metals
Metals
ANSWER : In graphite, bonding is
37.Thermonic emission occurs in
vacuum tubes
copper conductors
ferrite cores
transistors
ANSWER : : vacuum tubes
38.A good electric contact material should have all of the following properties excePt
high resistivity
high resistance to corrosion
good thermal conductivity
high melting point
ANSWER : : high resistivity
39.Solder is an alloy of
copper and aluminium
tin and lead
nickel, copper and zinc
silver, copper and lead
ANSWER : : tin and lead
40.______ is an example of piezoelectric material.
Glass
Quartz
Corrundum
Neoprene
ANSWER : : Quartz
41.The number of atoms per unit cell in B.C.C. structure is
1
2
4
8
ANSWER : : 2
42.Thermonic emission occurs in
vacuum tubes
copper conductors
ferrite cores
transistors
ANSWER : : vacuum tubes
43.A good electric contact material should have all of the following properties excePt
high resistivity
high resistance to corrosion
good thermal conductivity
high melting point
ANSWER : : high resistivity
44.Solder is an alloy of
copper and aluminium
tin and lead
nickel, copper and zinc
silver, copper and lead
ANSWER : : tin and lead
45.______ is an example of piezoelectric material.
Glass
Quartz
Corrundum
Neoprene
ANSWER : : Quartz
46.The number of atoms per unit cell in B.C.C. structure is
1
2
4
8
ANSWER : : 2
47.Overhead telephone wires are made of
aluminium
steel
ACSR conductors
copper
ANSWER : s: b
48.In thermocouples which of the following pairs is commonly used ?
Copper-constantan
Aluminium-tin
Silver-German silver
Iron-steel
ANSWER : : Copper-constantan
49.Which of the following affect greatly the resistivity of electrical conductors ?
Composition
Pressure
Size
Temperature
ANSWER : : Composition
50.Piezoelectric materials serve as a source of _____ .
resonant waves
musical waves
microwaves
ultrasonic waves
ANSWER : : ultrasonic waves
51.Non-linear resistors
produce harmonic distortion
follows Ohm’s law at low tempera�tures only
result in non-uniform heating
none of the above
ANSWER : : produce harmonic distortion
52.________ has the best damping properties.
Diamond
High speed steel
Mild steel
Cast iron
ANSWER : : Cast iron
53.Due to which of the following reasons copper and aluminium are not used for heating elements ?
Both have great tendency for oxidation
Both have low melting point
Very large length of wires will be required
All of the above
ANSWER : : All of the above
54.Carbon resistors are used extensively because they are
easy to make
compact
inexpensive
all of the above reasons
ANSWER : : all of the above reasons
55.Which of the following materials is the best conductor of electricity ?
Tungsten
Aluminium
Copper
Carbon
ANSWER : : Copper
56.The photo-electric effect occurs only when the incident light has more than a certain critical
intensity
speed
frequency
wave length
ANSWER : : frequency
57.Due to which of the following reasons aluminium does not corrode in atmost phere ?
Aluminium is a noble metal
Atmospheric oxygen can only diffuse very slowly through the oxide layer which is formed on the surface of aluminium
No reaction with oxygen occurs ft Any of the above
b
ANSWER : The impurity atoms is semiconductors
58.Due to which of the following fact, in India, aluminium is replacing copper ?
Aluminium is more ductile and malleable than copper
Aluminium is available in plenty, cheaper and lighter than copper
Aluminium has lower resistivity than that of copper
Aluminium has less temperature co-efficient than copper
ANSWER : : Aluminium is available in plenty, cheaper and lighter than copper
59.Thermocouples are mainly used for the measurement of
temperature
resistance
eddy currents
coupling co-efficient
ANSWER : : temperature
60.Which of the following high resistance materials has the highest operating temperature ?
Kanthal
Manganin
Nichrome
Eureka
ANSWER : : Kanthal
61.The resistivity of a metal is a function of temperature because
the amplitude of vibration of the atoms varies with temperature
the electron density varies with temperature
the electron gas density varies with temperature
the amplitude of vibration of the atoms varies with temperature
ANSWER : In a crystal, an atom vibrates at a frequency determined by
62.Substances whose specific resistance abruptly decreases at very low temperature are called
insulators
conductors
semiconductors
superconductors
ANSWER : : superconductors
63.Which of the following material is not a semiconductor ?
Silica
Germanium
Selenium
Gallium-arsenide
ANSWER : : Silica
64.Selenium is _____ semiconductor.
extrnisic
intmisic
N-type
P-type
ANSWER : : intmisic
65.Which of the following materials is used for making coils of standard resistances ?
Copper
Nichrome
Platinum
Manganin
ANSWER : : Manganin
66.Low resistivity materials are used in
transformer, motor and generator windings
transmission and distribution lines
house wiring
all above applications
ANSWER : : all above applications
67.Carbon rods are used in wet and dry cells because
carbon rod serves as conductor
carbon can resist the attack of bat�tery acid
both (a) and (b)
either (a) or (b)
ANSWER : : both (a) and (b)
68.Which of the following are non-conductors of electricity?
Non-metal solids except carbon
Air and most other gases
Pure water and liquids in general except mercury
All of the above
ANSWER : : All of the above
69.is the property of absorbing moisture from atmosphere.
Solubility
Viscosity
Porosity
Hygroscopicity
ANSWER : : Hygroscopicity
70.The conduction of electricity, in semiconductors, takes place due to movement of
positive ions only
negative ions only
positive and negative ions
electrons and holes
ANSWER : : electrons and holes
71.Which of the following is a semiconductor material ?
Phosphorous
Rubber
Silicon
Aluminium
ANSWER : : Silicon
72.Copper, even though costly, finds use in the windings of electrical machines because
copper points offer low contact resistance
copper can be easily soldered and welded
copper windings are less bulky and the machines become compact
all of the above
ANSWER : s: d
73.Carbon bearings are used under which of the following conditions ?
Where lubrication is difficult or im-possible
Where corrosive chemical action exists
Where high temperature exists
All of the above
ANSWER : : All of the above
74.Steel wire is used as
overhead telephone wire
earth wire
core wire of ACSR
all of the above
ANSWER : : all of the above
75.Which of the following is an advantage of stranded conductor over equivalent single conductor ?
Less liability to kink
Greater flexibility
Less liability to break
All of the above
ANSWER : : All of the above
76.is an element used in semiconductors whose atoms have three valence electrons.
An acceptor
A donor
Germanium
Silicon
ANSWER : : An acceptor
77.The minority carrier concentration is largely a function of
forward biasing voltage
reverse biasing voltage
temperature
the amount of doping
ANSWER : : temperature
78.The current due to electron flow in conduction band is the hole current in valence band.
equal to
less than
greater than
any of the above
ANSWER : : greater than
79.For a hole which of the following statements is incorrect ?
Holes can exist in certain semicon-ductors only
Holes can exist in any material in-cluding conductors
Holes may constitute an electric current
Holes can be considered as a net positive charge
ANSWER : : Holes can exist in any material in-cluding conductors
80.In conductors conduction of electricity takes place due to movement of
electrons only
positive ions only
negative ions only
positive and negative ions
ANSWER : : electrons only
81.The conductivity of an extrinsic semiconductor with temperature
decreases
increases
remains constant
none of the above
ANSWER : : remains constant
82.For a particular material the Hall coefficient was found to be zero. The material is
insulator
metal
intrinsic semiconductor
none of the above
ANSWER : : metal
83.The forbidden gap in an insulator is
large
small
nil
any of the above
ANSWER : : large
84.The carbon percentage is least in
low carbon steel
wrought iron
cast iron
malleable iron
ANSWER : : wrought iron
85.For germanium the forbidden energy gap is
0.15 eV
0.25 eV
0.5eV
0.7eV
ANSWER : s: d
86.Superconducting metal in super conducting state has relative permeability of
zero
one
negative
more than one
ANSWER : : zero
87.Surface resistance of an insulating material is reduced due to the
smoky and dirty atmosphere
humidity in the atmosphere
both (a) and (b)
neither (a) nor (b)
ANSWER : : both (a) and (b)
88.Spark plug makes use of which of the following materials for insulation ?
Porcelain
Slate
Asbestos
Glass
ANSWER : : Porcelain