In this article, we shared the electrical engineering materials objective questions and answers for electrical and electronics engineers.
Electrical Engineering Materials Objective Questions
The below list provides all the multiple-choice questions related to engineering materials.
Answers are available at the bottom of the article.
1. The current due to electron flow in the conduction band is ____ the hole current in the valence band.
| A) | any of these answers |
| B) | less than |
| C) | greater than |
| D) | equal to |
2. Effect of moisture on the insulating materials is to
| A) | increase dielectric loss |
| B) | all of these answers |
| C) | decrease dielectric constant |
| D) | decrease dielectric strength |
| E) | decrease insulation resistance |
3. Insulators have which of the following?
| A) | A full valence band |
| B) | A large energy gap |
| C) | All of these answers |
| D) | An empty conduction band |
4. Which of the following is a semiconductor material?
| A) | Aluminium |
| B) | Rubber |
| C) | Phosphorous |
| D) | Silicon |
5. The co-ordination number of a simple cubic structure is
| A) | 4 |
| B) | 6 |
| C) | 2 |
| D) | 8 |
6. The dielectric strength of paper is
| A) | 4 to 10 kV/mm thickness |
| B) | 15 to 20 kV/mm thickness |
| C) | 12 to 15 kV/mm thickness |
| D) | 2 to 4 kV/mm thickness |
7. A carbon resistor contains
| A) | finely divided carbon black |
| B) | solid carbon granules |
| C) | carbon crystals |
| D) | pulverized coal |
8. ____ is viscoelastic.
| A) | Graphite |
| B) | Glass |
| C) | Cast-iron |
| D) | Rubber |
9. The photo-electric effect occurs only when the incident light has more than a certain critical
| A) | speed |
| B) | wave length |
| C) | frequency |
| D) | intensity |
10. The ideal core material for small reactors and transformers employed in communication equipment should possess which of the following characteristics?
| A) | All of these answers |
| B) | Small hysteresis loss |
| C) | Constant permeability |
| D) | Small eddy current loss within the range of small magnetizing forces and over the wide range of frequencies met in such applications |
11. The ionically and covalently bonded materials are known as
| A) | either insulators or poor conductors |
| B) | poor conductors |
| C) | insulators |
| D) | none of these answers |
12. The conductivity of semiconductors depends on which of the following factors?
| A) | Both Number of current carriers present per unit volume and The mobility of the current carriers |
| B) | None of these answers |
| C) | The mobility of the current carriers |
| D) | Number of current carriers present per unit volume |
13. Germanium possesses
| A) | four valence electrons |
| B) | two valence electrons |
| C) | three valence electrons |
| D) | five valence electrons |
14. Thermocouples are mainly used for the measurement of
| A) | temperature |
| B) | eddy currents |
| C) | coupling co-efficient |
| D) | resistance |
15. The dielectric losses occur in all solid and liquid dielectrics due to which of the following?
| A) | None of these answers |
| B) | Hysteresis |
| C) | Both Conduction current and Hysteresis |
| D) | Conduction current |
16. The formula ____ determines the number of electrons that can be accommodated at any level.
| A) | 4n3 |
| B) | 4n2 |
| C) | 2n2 |
| D) | 2n3 |
17. Selenium is ____ semiconductor.
| A) | P-type |
| B) | intrnisic |
| C) | extrnisic |
| D) | N-type |
18. The magnetic domains, during the process of magnetisation of ferromagnetic material
| A) | rotate first and then expand |
| B) | expand first and then rotate |
| C) | neither expand nor rotate |
| D) | only expand |
19. In a P.N.P. transistor majority charge carriers are
| A) | holes |
| B) | electrons |
| C) | both electrons and holes |
| D) | either electrons or holes |
20. The eddy currents produce a magnetic field of their own which ____ the main field.
| A) | does not affect |
| B) | assists |
| C) | none of these answers |
| D) | opposes |
21. High-frequency transformers cores are generally made from
| A) | mu-metal |
| B) | mone-metal |
| C) | ferrites |
| D) | none of these answers |
22. Fahy permeameter entails which of the following advantages?
| A) | All of these answers |
| B) | Simple in both construction and operation as compared with Burrow’s permeameter |
| C) | Requires only one test specimen |
| D) | Less sensitive to the effects of magnetic inhomogeneities in the specimen |
23. In carbon steel if the percentage of carbon is increased it has which of the following effects?
| A) | Resistivity is increased |
| B) | Permeability is decreased |
| C) | The saturation temperature is lowered |
| D) | Co-ercive force and retentivity is increased |
| E) | All of these answers |
24. The conductivity of an extrinsic semiconductor ____ with temperature
| A) | increases |
| B) | decreases |
| C) | remains constant |
| D) | none of these answers |
25. In a P.N.P. transistor the collector current is always
| A) | greater than the emitter current |
| B) | none of these answers |
| C) | less than the emitter current |
| D) | equal to the emitter current |
26. In an intrinsic semiconductor
| A) | there are no holes in the material |
| B) | there are no electrons in the material |
| C) | the number of holes is too small |
| D) | electrons is the material are neutralised by the holes |
27. In ____ semiconductor, the Fermi level lies midway between the conduction and valence bands.
| A) | intrinsic |
| B) | N-type |
| C) | both P-type and N-type |
| D) | P-type |
28. Platinum is used in
| A) | thermocouple |
| B) | electrical contacts |
| C) | grids of special purpose vacuum tubes |
| D) | all of these answers |
| E) | heating element in high temperature furnace |
29. Carbon electrodes are not used in
| A) | GLS lamps |
| B) | cinema projectors |
| C) | dry cells |
| D) | electric arc furnace |
30. For a hole which of the following statements is incorrect?
| A) | Holes may constitute an electric current |
| B) | Holes can exist in any material including conductors |
| C) | Holes can be considered as a net positive charge |
| D) | Holes can exist in certain semiconductors only |
31. The change of resistance in a magnetic field is called the
| A) | photo-electric effect |
| B) | magneto-resistance effect |
| C) | none of these answers |
| D) | Seebeck effect |
32. Which of the following is the poorest conductor of electricity?
| A) | Aluminium |
| B) | Steel |
| C) | Silver |
| D) | Carbon |
33. Which of the following materials does not have covalent bonds?
| A) | Metals |
| B) | Organic polymers |
| C) | Silicon |
| D) | none of these answers |
34. The transition temperature of mercury is
| A) | 9.22°K |
| B) | 4.12°K |
| C) | 1.14°K |
| D) | 18.0°K |
35. The conductors have transport phenomena of electrons due to
| A) | magnetic field |
| B) | none of these answers |
| C) | electric field |
| D) | electromagnetic field |
36. ___ is the property of absorbing moisture from the atmosphere.
| A) | Viscosity |
| B) | Hygroscopicity |
| C) | Porosity |
| D) | Solubility |
37. Commonly used conducting materials are
| A) | copper and silver |
| B) | copper |
| C) | platinum and gold |
| D) | aluminium |
| E) | both copper and aluminium |
38. For which of the following materials the relative permeability is much greater than unity?
| A) | Diamagnetic materials |
| B) | Ferromagnetic materials |
| C) | None of these answers |
| D) | Paramagnetic materials |
39. The permeability of iron is around
| A) | 500 |
| B) | 1200 |
| C) | 800 |
| D) | 2000 |
40. ____ has zero temperature coefficient of resistance.
| A) | Carbon |
| B) | Manganin |
| C) | Porcelain |
| D) | Aluminium |
41. Which of the following materials is preferred for transmitting electrical energy over long distance?
| A) | Aluminium |
| B) | Copper |
| C) | Steel reinforced aluminium |
| D) | Steel reinforced copper |
42. ___ is that property of the material that opposes the production of magnetic flux in it
| A) | Magnetic reluctance |
| B) | Retentivity |
| C) | Remanance |
| D) | Susceptibility |
43. Insulation resistance ____ with the increase in temperature.
| A) | none of these answers |
| B) | decreases |
| C) | increases |
| D) | remains unaffected |
44. Electronegative gases are
| A) | inflammable |
| B) | non-explosive |
| C) | both inflammable and non-explosive |
| D) | none of these answers |
45. Thermistors possess
| A) | a negative temperature resistivity of high absolute value |
| B) | zero resistivity |
| C) | none of these answers |
| D) | a positive temperature resistivity of high absolute value |
46. In conductors conduction of electricity takes place due to the movement of
| A) | positive and negative ions |
| B) | positive ions only |
| C) | negative ions only |
| D) | none of these answers |
| E) | electrons only |
47. Curie temperature is the temperature above which a ferromagnetic material becomes
| A) | diamagnetic |
| B) | paramagnetic |
| C) | none of these answers |
| D) | either paramagnetic or diamagnetic |
48. The dielectric susceptibility determines the value of the
| A) | dielectric strength |
| B) | dielectric constant |
| C) | both dielectric constant and dielectric strength |
| D) | none of these answers |
49. In a semiconductor the resistivity decreases ____ with temperature,
| A) | non-linearly |
| B) | any of these answers |
| C) | exponentially |
| D) | linearly |
50. The power arc following a flashover or the breaking of contacts over the insulator surface subjects the surface to which of the following?
| A) | Deposition of electrode material |
| B) | All of these answers |
| C) | Extreme heat |
| D) | Chemical action |
51. The function of insulating liquids is
| A) | to provide heat transfer |
| B) | none of these answers |
| C) | both to provide electrical insulation and to provide heat transfer |
| D) | to provide electrical insulation |
52. Superconductivity can be destroyed by
| A) | adding impurities |
| B) | any of these answers |
| C) | reducing temperatures |
| D) | application of magnetic field |
53. Ferroelectric materials have which of the following characteristics?
| A) | They exhibit hysteresis loops |
| B) | Both They have a high dielectric constant which is nonlinear & They exhibit hysteresis loops |
| C) | None of these answers |
| D) | They have a high dielectric constant which is nonlinear |
54. Which of the following is an advantage of stranded conductors over equivalent single conductors?
| A) | Less liability to kink |
| B) | All of these answers |
| C) | Less liability to break |
| D) | Greater flexibility |
55. Thermistors find use in which of the following?
| A) | As a thermal relay |
| B) | All of these answers |
| C) | In control devices actuated by temperature changes |
| D) | In thermometry |
| E) | In the measurement of microwave power |
56. Ferro-materials are the dielectrics analogous to
| A) | diamagnetic materials |
| B) | none of these answers |
| C) | paramagnetic materials |
| D) | ferromagnetic materials |
57. Copper, even though costly, finds use in the windings of electrical machines because
| A) | copper windings are less bulky and the machines become compact |
| B) | all of these answers |
| C) | copper can be easily soldered and welded |
| D) | copper points offer low contact resistance |
58. The kinetic energy of a bounded electron is
| A) | equal to that of unbounded electron |
| B) | less than that of unbounded electron |
| C) | greater than that of unbounded electron |
| D) | none of these answers |
| E) | infinite |
59. Which of the following is a consequence of ionisation?
| A) | Carbonisation, decomposition and mechanical damage to the insulating material |
| B) | A great power loss in the insulation |
| C) | Thermal instability |
| D) | All of these answers |
| E) | Lowering of the breakdown voltage of the insulation |
60. If the domain walls in a magnetic material can be easily moved the material displays
| A) | high flux density |
| B) | none of these answers |
| C) | high permeability |
| D) | permanent magnetic behaviour |
61. The metal having the lowest temperature coefficient of resistance is
| A) | copper |
| B) | aluminium |
| C) | kanthal |
| D) | gold |
62. Flashpoint temperature of fresh dry oil is
| A) | 135°C |
| B) | 75°C |
| C) | 55°C |
| D) | 100°C |
63. High resistivity materials are used in
| A) | all of these answers |
| B) | motor starters |
| C) | heating elements |
| D) | incandescent lamps |
| E) | precision instrument |
64. Superconductors are becoming popular for use in
| A) | manufacture of bubble memories |
| B) | generating very strong magnetic field |
| C) | generating regions free from magnetic field |
| D) | generating electrostatic field |
65. When the temperature exceeds a certain value called the Curie point, the substance
| A) | loses its ferro-electric properties |
| B) | gains ferro-electric properties |
| C) | none of these answers |
| D) | either loses its ferro-electric properties or gains ferro-electric properties |
66. Which of the following materials is used for making coils of standard resistances?
| A) | Nichrome |
| B) | Manganin |
| C) | Copper |
| D) | Platinum |
67. Superconducting metal in super conducting state has a relative permeability of
| A) | one |
| B) | more than one |
| C) | zero |
| D) | negative |
68. ___ is the most detrimental impurity in magnetic materials.
| A) | Carbon |
| B) | Oxygen |
| C) | Nitrogen |
| D) | Sulphur |
69. At transition temperature the value of the critical field is
| A) | complex value |
| B) | zero |
| C) | positive real value |
| D) | negative real value |
70. As compared to thermionic tubes, transistors claim which of the following advantages?
| A) | Long life if operated within the permissible limits of temperature |
| B) | Operating voltage quite low |
| C) | Compact size, light in weight |
| D) | All of these answers |
| E) | Instantaneous operation |
71. The moisture absorbed by an insulating material causes which of the following?
| A) | All of these answers |
| B) | Decrease in dielectric strength due to change in field distribution within the insulating material |
| C) | A decrease in the volume resistivity, especially surface resistivity |
| D) | An increase in the dissipation factor and a certain increase in dielectric constant |
72. Constantan contains
| A) | tungsten and silver |
| B) | copper and tungsten |
| C) | copper and nickel |
| D) | silver and tin |
73. If the resistance of a conductor does not vary in accordance with Ohm’s law it is known as
| A) | reverse conductor |
| B) | bad-conductor |
| C) | non-conductor |
| D) | non-linear conductor |
74. Which of the following kind of breakdown is possible in solid dielectrics?
| A) | Electrothermal breakdown |
| B) | All of these answers |
| C) | Purely electrical breakdown |
| D) | Electrochemical breakdown |
75. A pure semiconductor, under ordinary conditions, behaves like
| A) | a ferroelectric material |
| B) | a magnetic material |
| C) | an insulator |
| D) | a conductor |
76. The value of the critical field below the transition temperature will
| A) | remain unchanged |
| B) | increase |
| C) | decrease |
| D) | any of these answers |
77. The number of atoms per unit cell in B.C.C. structure is
| A) | 4 |
| B) | 2 |
| C) | 1 |
| D) | 8 |
78. Presence of even a trace of water in transformer oil ____ its insulation strength considerably.
| A) | does not affect |
| B) | none of these answers |
| C) | reduces |
| D) | increases |
79. The dielectric strength of mica varies from
| A) | 10 to 20 kV/mm thickness |
| B) | 30 to 40 kV/mm thickness |
| C) | 40 to 150 kV/mm thickness |
| D) | 20 to 30 kV/mm thickness |
80. A ferroelectric material contains small regions which are polarised in different directions even in the ____ of an electric field.
| A) | either absence or presence |
| B) | presence |
| C) | absence |
| D) | none of these answers |
81. The change in dimensions during the process of magnetisation is called
| A) | magnetostriction |
| B) | none of these answers |
| C) | Hall’s effect |
| D) | skin effect |
| E) | Seebeck effect |
82. The ratio of the intensity of magnetisation to magnetising force is called
| A) | magnetic potential |
| B) | permeability |
| C) | none of these answers |
| D) | susceptibility |
83. For germanium the forbidden energy gap is
| A) | 0.25 eV |
| B) | 0.7 eV |
| C) | 0.15 eV |
| D) | 0.5 eV |
84. The readiness of a material to accept magnetism is expressed by its
| A) | either permeability or permittivity |
| B) | none of these answers |
| C) | permittivity |
| D) | permeability |
85. Most of the common metals have ____ structure.
| A) | cubic |
| B) | hexagonal |
| C) | linear |
| D) | orthorhombic |
86. Insulating gases entail which of the following major problems?
| A) | Temperature instability |
| B) | Fire hazards |
| C) | All of these answers |
| D) | Abnormalities in dielectric behaviour at high pressures |
87. The resistivity of the insulator ____ in the presence of moisture.
| A) | none of these answers |
| B) | is considerably increased |
| C) | is considerably lowered |
| D) | remains unaffected |
88. For ferromagnetic materials the susceptibility
| A) | none of these answers |
| B) | is zero |
| C) | is not constant |
| D) | is constant |
89. Due to which of the following reasons aluminium does not corrode in the atmosphere?
| A) | No reaction with oxygen occurs |
| B) | Aluminium is a noble metal |
| C) | Any of these answers |
| D) | Atmospheric oxygen can only diffuse very slowly through the oxide layer which is formed on the surface of aluminium |
90. The carbon percentage is least in
| A) | cast iron |
| B) | wrought iron |
| C) | low carbon steel |
| D) | malleable iron |
91. Piezoelectric materials serve as a source of____
| A) | musical waves |
| B) | ultrasonic waves |
| C) | microwaves |
| D) | resonant waves |
92. When radiation is incident on a semiconductor, its conductivity increases, this effect is called
| A) | none of these answers |
| B) | Seebeck effect |
| C) | Hall effect |
| D) | photo conductive effect |
93. A highly conductive material must have
| A) | good corrosion resistance |
| B) | all of these answers |
| C) | easy solderable and drawable quality |
| D) | highest conductivity and lowest temperature co-efficient |
| E) | good mechanical strength |
94. For a particular material the Hall coefficient was found to be zero. The material is
| A) | intrinsic semiconductor |
| B) | metal |
| C) | insulator |
| D) | none of these answers |
95. If the centre of gravity of the positive and negative charges in the body do not coincide in the absence of an applied electric field, the substance has an electric dipole moment and is said to be spontaneously polarised. Such a substance is called
| A) | conductor |
| B) | dielectric |
| C) | ferro-electric |
| D) | insulator |
96. Practically all organic substances are
| A) | diamagnetic |
| B) | none of these answers |
| C) | ferro-magnetic |
| D) | paramagnetic |
97. The dielectric strength of asbestos is
| A) | 3 to 4.5 kV/mm thickness |
| B) | 8 to 9.5 kV/mm thickness |
| C) | 5 to 6.5 kV/mm thickness |
| D) | 1.5 to 2.5 kV/mm thickness |
98. In a crystal, an atom vibrates at a frequency determined by
| A) | none of these answers |
| B) | the temperature of the crystal |
| C) | the heat content of the crystal |
| D) | the stiffness of the bonds it makes with neighbours |
99. ___ is an example of piezoelectric material.
| A) | Neoprene |
| B) | Quartz |
| C) | Glass |
| D) | Corrundum |
100. The dielectric loss is affected by which of the following factors?
| A) | Voltage increase |
| B) | Temperature rise |
| C) | All of these answers |
| D) | Frequency of applied voltage |
| E) | Presence of humidity |
101. Which of the following conditions go a long way in causing the electrothermal breakdown of the dielectric?
| A) | Large dielectric loss |
| B) | High temperature of both the dielectric and the surrounding medium |
| C) | Continuous application of high voltage |
| D) | All of these answers |
| E) | Large thickness of the dielectric |
102. The conductivity of a conductor can be increased by
| A) | increasing its vibration |
| B) | decreasing its temperature |
| C) | increasing its temperature |
| D) | decreasing its vibration |
103. The value of steinmetz co-efficient k is approximately ____ for all modern magnetic materials.
| A) | 1.4 |
| B) | 3 |
| C) | 2 |
| D) | 1.2 |
104. The insulating materials to be used for most of electronic equipment should possess which of the following characteristics?
| A) | Arc resistance |
| B) | Thermal stability |
| C) | High mechanical strength |
| D) | High electric strength |
| E) | All of these answers |
105. The coils of D.C. motor starter are wound with wire of
| A) | kanthal |
| B) | manganin |
| C) | nichrome |
| D) | copper |
106. Overhead telephone wires are made of
| A) | steel |
| B) | aluminium |
| C) | ACSR conductors |
| D) | copper |
107. The dielectric strength of gaseous dielectrics depends on which of the following factors?
| A) | Polarity of electrodes |
| B) | Frequency of applied field |
| C) | All of these answers |
| D) | Pressure |
| E) | Uniformity of applied electric field |
108. ___ is an element used in .semiconductors whose atoms have three valence electrons.
| A) | A donor |
| B) | Germanium |
| C) | An acceptor |
| D) | Silicon |
109. The conduction of electricity, in semiconductors, takes place due to the movement of
| A) | negative ions only |
| B) | electrons and holes |
| C) | positive and negative ions |
| D) | positive ions only |
110. The ____ polarisation vanishes at Curie temperature of the material.
| A) | spontaneous |
| B) | dipolar |
| C) | none of these answers |
| D) | ionic |
111. The structure sensitive property of a superconductor is
| A) | none of these answers |
| B) | critical current density |
| C) | critical magnetic field |
| D) | transition temperature |
112. Which of the following materials is the best conductor of electricity?
| A) | Tungsten |
| B) | Carbon |
| C) | Aluminium |
| D) | Copper |
113. A good electric contact material should have all of the following properties except
| A) | good thermal conductivity |
| B) | high resistance to corrosion |
| C) | high melting point |
| D) | high resistivity |
114. The converse of hardness is known as
| A) | none of these answers |
| B) | toughness |
| C) | softness |
| D) | malleability |
115. Uniaxial anisotropy can be induced in bulk materials by which of the following methods?
| A) | Magnetic quenching |
| B) | Magnetic annealing |
| C) | Cold working |
| D) | All of these answers |
116. Non-linear resistors
| A) | follows Ohm’s law at low temperatures only |
| B) | produce harmonic distortion |
| C) | result in non-uniform heating |
| D) | none of these answers |
117. Which of the following is not a ferroelectric material?
| A) | Brass |
| B) | Rochelle salt |
| C) | Lead zirconate |
| D) | Barium titanate |
118. The covalent bond is formed by
| A) | sharing of a variable number of electrons by a variable number of atoms |
| B) | none of these answers |
| C) | sharing of electrons between atoms |
| D) | transfer of electrons between atoms |
119. The resistivity of a metal is a function of temperature because
| A) | none of these answers |
| B) | the electron gas density varies with temperature |
| C) | the amplitude of vibration of the atoms varies with temperature |
| D) | the electron density varies with temperature |
120. Photo-voltaic cells find applications in which of the following?
| A) | All of these answers |
| B) | Television circuits |
| C) | Automatic control systems |
| D) | Sound motion picture recording and reproducing equipment |
121. The major use of ferro-electrics is in ____
| A) | none of these answers |
| B) | active transducers |
| C) | electro-mechanical transducers |
| D) | passive transducers |
122. Due to which of the following reasons copper and aluminium are not used for heating elements?
| A) | Both have great tendency for oxidation |
| B) | Very large length of wires will be required |
| C) | All of these answers |
| D) | Both have low melting point |
123. A good insulating material should possess which of the following characteristics?
| A) | Low dissipation factor (loss tangent) |
| B) | All of these answers |
| C) | Least thermal expansion |
| D) | High dielectric strength |
| E) | Large insulation resistance |
124. ____ is a hard solder.
| A) | None of these answers |
| B) | Tin-lead |
| C) | Tin-silver-lead |
| D) | Copper-zinc |
125. Carbon resistors are used extensively because they are
| A) | compact |
| B) | easy to make |
| C) | all of these answers |
| D) | inexpensive |
126. Polarisation is
| A) | a vector quantity |
| B) | both a scalar quantity and a vector quantity |
| C) | none of these answers |
| D) | a scalar quantity |
127. Spark plug makes use of which of the following materials for insulation?
| A) | Porcelain |
| B) | Glass |
| C) | Asbestos |
| D) | Slate |
128. Which of the following is a ferro-electric material?
| A) | Y-alloy |
| B) | Stainless steel |
| C) | Wrought iron |
| D) | Boron nitride |
129. ____ is a negatively charged particle present in an atom.
| A) | Neutron |
| B) | Electron |
| C) | None of these answers |
| D) | Proton |
130. Solder is an alloy of
| A) | nickel, copper and zinc |
| B) | copper and aluminium |
| C) | silver, copper and lead |
| D) | tin and lead |
131. The superconductivity is due to
| A) | all electrons interact in the superconducting state |
| B) | the electrons jump into nucleus at 0°K |
| C) | none of these answers |
| D) | the crystal structure having no atomic vibration at 0°K |
132. An H.R.C. fuse is
| A) | a wire of platinum |
| B) | a ceramic tube having carbon rod inside it |
| C) | a ceramic body having metal and caps |
| D) | a heavy cross-section of copper or aluminium |
133. Conduction of heat in a semiconductor takes place in which of the following ways?
| A) | By the thermal vibrations of the atoms |
| B) | By the electrons |
| C) | None of these answers |
| D) | Both By the thermal vibrations of the atoms and By the electrons |
134. The conductivity of a metal is determined by
| A) | none of these answers |
| B) | the electronic concentration and the mobility of the free electrons |
| C) | either the electronic concentration and the mobility of the free electrons or the number of valence electrons per atom |
| D) | the number of valence electrons per atom |
135. Surface resistance of insulating material is reduced due to the
| A) | humidity in the atmosphere |
| B) | both smoky and dirty atmosphere and humidity in the atmosphere |
| C) | smoky and dirty atmosphere |
| D) | neither smoky and dirty atmosphere nor humidity in the atmosphere |
136. Most of the common metals have ____ structure.
| A) | hexagonal |
| B) | orthorhombic |
| C) | linear |
| D) | cubic |
137. In graphite, bonding is
| A) | Vander Waals |
| B) | covalent |
| C) | metallic |
| D) | Vander Waals and covalent |
138. In thermocouples which of the following pairs is commonly used?
| A) | Aluminium-tin |
| B) | Copper-constantan |
| C) | Iron-steel |
| D) | Silver-German silver |
139. ____ breakdown normally occurs when the temperature is very high and surrounding air has high humidity.
| A) | Purely electrical |
| B) | none of these answers |
| C) | Electrothermal |
| D) | Electrochemical |
140. Which of the following insulating material is in connnon use for overhead power lines?
| A) | None of these answers |
| B) | Both Porcelain & Toughened glass |
| C) | Porcelain |
| D) | Toughened glass |
141. ____ materials have relative permeability slightly less than unity
| A) | Paramagnetic |
| B) | None of these answers |
| C) | Ferro-magnetic |
| D) | Diamagnetic |
142. The impurity atoms is semiconductors
| A) | inject more charge carriers |
| B) | increase the kinetic energy of valence electrons |
| C) | reduce the energy gap |
| D) | all of these answers |
143. In a superconductor, the value of critical density depends upon
| A) | temperature |
| B) | both magnetic field strength and temperature |
| C) | either magnetic field strength or temperature |
| D) | magnetic field strength |
144. Due to which of the following factors the brush wear rate is altered?
| A) | Surface conditions of brush and commutator |
| B) | Contact pressure |
| C) | Speed of the machine |
| D) | All of these answers |
| E) | Excessive sparking |
145. Dielectrics have
| A) | many free electrons |
| B) | a few free electrons |
| C) | none of these answers |
| D) | no free electrons |
146. Alnico magnet alloys have the ____ energy per unit of cost or volume of any permanent magnet material commercially available.
| A) | none of these answers |
| B) | either highest or lowest |
| C) | lowest |
| D) | highest |
147. ___ is the main constituent of glass
| A) | Al2O3 |
| B) | Fe2O3 |
| C) | SiO2 |
| D) | B2O3 |
148. Dielectric materials are essentially
| A) | conducting materials |
| B) | semiconducting materials |
| C) | ferro-electric material |
| D) | insulating materials |
149. Rochelle salt has
| A) | one Curie point |
| B) | none of these answers |
| C) | three Curie points |
| D) | two Curie points |
150. Which of the following factors affect the resistivity of metals?
| A) | All of these answers |
| B) | Alloying |
| C) | Cold work |
| D) | Temperature |
| E) | Age hardening |
151. ____ is most commonly used for making magnetic recording tape
| A) | Silicon-iron |
| B) | Silver nitrate |
| C) | Ferric oxide |
| D) | Small particles of iron |
152. Carbon rods are used in wet and dry cells because
| A) | either carbon rod serves as conductor or carbon can resist the attack of battery acid |
| B) | carbon rod serves as conductor |
| C) | carbon can resist the attack of battery acid |
| D) | both carbon rod serves as conductor and carbon can resist the attack of battery acid |
153. Substances whose specific resistance abruptly decreases at very low temperature are called
| A) | insulators |
| B) | conductors |
| C) | semiconductors |
| D) | superconductors |
154. Mercury as an electric contact material is
| A) | a gas |
| B) | a metal |
| C) | a liquid |
| D) | a metal liquid |
155. By which of the following methods the insulation can be protected against moisture?
| A) | Hermetic sealing |
| B) | Impregnation of winding |
| C) | All of these answers |
| D) | Making insulation hydrophobic (water proof) |
156. Which of the following resistive materials has the lowest temperature coefficient of resistance?
| A) | Kanthal |
| B) | Nichrome |
| C) | Constantan |
| D) | Molybdenum. |
157. Mica is usually avoided for slot linings of high voltage machines because its
| A) | none of these answers |
| B) | space factor is low |
| C) | space factor is high |
| D) | space factor is nil |
158. A thermistor has ____ temperature coefficient of resistance
| A) | a positive |
| B) | zero |
| C) | any of these answers |
| D) | a negative |
159. The minority carrier concentration is largely a function of
| A) | temperature |
| B) | forward biasing voltage |
| C) | reverse biasing voltage |
| D) | the amount of doping |
160. The value of dielectric strength is useful in which of the following?
| A) | Determining the effect of environmental and operating conditions |
| B) | Measuring uniformity |
| C) | All of these answers |
| D) | Comparing insulating materials |
161. In a semiconductor, the hole formed is a
| A) | none of these answers |
| B) | positive charge carrier |
| C) | either positive charge carrier or negative charge carrier |
| D) | negative charge carrier |
162. The total number of crystal systems is
| A) | 2 |
| B) | 12 |
| C) | 4 |
| D) | 7 |
163. Steel wire is used as
| A) | earth wire |
| B) | overhead telephone wire |
| C) | all of these answers |
| D) | core wire of ACSR |
164. Which of the following are non-conductors of electricity?
| A) | Pure water and liquids in general except mercury |
| B) | Air and most other gases |
| C) | Non-metal solids except carbon |
| D) | All of these answers |
165. The relative magnetisation under a given field ____ as the temperature approaches the Curie point.
| A) | none of these answers |
| B) | either decreases or increases |
| C) | decreases |
| D) | increases |
166. The tiny block formed by the arrangement of a small group of atoms is called the
| A) | unit cell |
| B) | either unit cell or space lattice |
| C) | none of these answers |
| D) | space lattice |
167. Which of the following factors cause magnetic ageing?
| A) | Changes in the external magnetic circuit, such as increasing the air gap length or removing the “keeper” |
| B) | Mechanical vibration |
| C) | Temperature condition |
| D) | All of these answers |
| E) | Presence of strong external fields |
168. Hall effect may be used for which of the following?
| A) | Magnetic field meter |
| B) | All of these answers |
| C) | Determining the carrier concentration |
| D) | Calculating the mobility, having measured the conductivity |
| E) | Determining whether a semiconductor is N-type or P-type |
169. Low resistivity materials are used in
| A) | house wiring |
| B) | transmission and distribution lines |
| C) | all of these answers |
| D) | transformer, motor and generator windings |
170. Non-linear resistors are also called
| A) | none of these answers |
| B) | varistors |
| C) | thermistors |
| D) | either thermistors or varistors |
171. The forbidden gap in an insulator is
| A) | small |
| B) | any of these answers |
| C) | large |
| D) | nil |
172. Superconductivity is observed for
| A) | frequencies having no effect |
| B) | infrared frequencies |
| C) | a.c. and high frequency |
| D) | none of these answers |
| E) | d.c. and low frequency |
173. Emitter arrow, in a transistor, shows the direction of
| A) | flow of conventional current |
| B) | electron flow |
| C) | none of these answers |
| D) | either flow of conventional current or electron flow |
174. Above the Curie temperature the materials have no ferro-electric properties and become ordinary
| A) | semiconducting materials |
| B) | insulating materials |
| C) | none of these answers |
| D) | conducting materials |
175. Which of the following high resistance materials has the highest operating temperature?
| A) | Nichrome |
| B) | Kanthal |
| C) | Manganin |
| D) | Eureka |
176. Which of the following gases is classified as electronegative?
| A) | Sulphur hexafluoride |
| B) | Propane |
| C) | Nitrogen |
| D) | Methane |
177. The materials having permanent electric moment are called
| A) | dielectrics |
| B) | antiferro-electric materials |
| C) | semiconducting materials |
| D) | electrets |
178. Which of the following tests is carried out on transformer oil?
| A) | Sludge resistance test |
| B) | Acidity test |
| C) | Electric strength test |
| D) | All of these answers |
| E) | Moisture test |
179. In ____ semiconductor, the Fermi level lies midway between the conduction and valence bands.
| A) | N-type |
| B) | P-type |
| C) | intrinsic |
| D) | both P-type and N-type |
180. Which of the following material is not a semiconductor?
| A) | Silica |
| B) | Gallium-arsenide |
| C) | Selenium |
| D) | Germanium |
181. ____ has the best damping properties.
| A) | Diamond |
| B) | Mild steel |
| C) | Cast iron |
| D) | High speed steel |
182. Which of the following affect greatly the resistivity of electrical conductors?
| A) | Composition |
| B) | Temperature |
| C) | Pressure |
| D) | Size |
183. On which of the following factors does the resistivity of a material depend?
| A) | Resistance of the conductor |
| B) | Area of the conductor section |
| C) | Length of the conductor |
| D) | All of these answers |
184. Insulators are the materials in which valence electrons are bounded
| A) | moderately to their parent atoms |
| B) | very tightly to their parent atoms |
| C) | loosely to their parent atoms |
| D) | none of these answers |
185. Capacitors with very high dielectric constants have been developed by treating BaTiO3 in
| A) | either an oxidising atmosphere or a reducing atmosphere |
| B) | a reducing atmosphere |
| C) | an oxidising atmosphere |
| D) | none of these answers |
186. Magnetically hard materials possess which of the following characteristics?
| A) | High retentivity |
| B) | All of these answers |
| C) | Strong magnetic reluctance |
| D) | High value of B.H. product |
| E) | High co-ercivity |
187. Which of the following variety of copper has the best conductivity?
| A) | Hard drawn copper |
| B) | Copper containing traces of silicon |
| C) | Induction hardened copper |
| D) | Pure annealed copper |
188. The spontaneous magnetisation is the most important characteristic of ____ materials.
| A) | any of these answers |
| B) | diamagnetic |
| C) | paramagnetic |
| D) | ferro-magnetic |
189. Due to which of the following fact, in India, aluminium is replacing copper?
| A) | Aluminium has less temperature co-efficient than copper |
| B) | Aluminium is more ductile and malleable than copper |
| C) | Aluminium has lower- resistivity than that of copper |
| D) | Aluminium is available in plenty, cheaper and lighter than copper |
190. Dielectric strength is expressed in
| A) | kV / mm3 |
| B) | kV / mm2 |
| C) | kV / mm |
| D) | none of these answers |
191. Which of the following processes is used to produce porcelain?
| A) | Any of these answers |
| B) | Dry process |
| C) | Wet process |
| D) | Casting process |
192. Carbon bearings are used under which of the following conditions?
| A) | Where lubrication is difficult or impossible |
| B) | All of these answers |
| C) | Where high temperature exists |
| D) | Where corrosive chemical action exists |
193. Which of the following effects is produced by ‘sludge’ formation?
| A) | Ducts are clogged |
| B) | All of these answers |
| C) | Increase in operating temperature results |
| D) | Rate of heat transfer is reduced |
194. The ferro-electric materials ____ Curie point have special properties.
| A) | above |
| B) | either below & above |
| C) | below |
| D) | none of these answers |
195. Porcelain insulators are employed for insulating terminals of
| A) | any of these answers |
| B) | high voltage machines |
| C) | medium voltage machines |
| D) | low voltage machines |
196. The behaviour of real dielectrics is primarily
| A) | both electrostatic and electromagnetic |
| B) | electrostatic |
| C) | none of these answers |
| D) | electromagnetic |
197. By increasing impurity content in the metal alloy the residual resistivity always
| A) | remains constant |
| B) | decreases |
| C) | increases |
| D) | becomes temperature independent |
198. A perfect conductor has
| A) | none of these answers |
| B) | unity conductivity |
| C) | infinite conductivity |
| D) | zero conductivity |
199. Thermonic emission occurs in
| A) | copper conductors |
| B) | transistors |
| C) | vacuum tubes |
| D) | ferrite cores |
200. In potassium Dihydrogen Phosphate the Curie points are
| A) | negative |
| B) | none of these answers |
| C) | positive |
| D) | either positive or negative |
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