101. Which material is used for making brushes of DC machines?
A) Copper
B) Graphite
C) Aluminum
D) Brass
Ans: B
102. The phenomenon of increase in resistance due to mechanical strain is known as
A) Piezoelectric effect
B) Magnetostriction
C) Piezoresistive effect
D) Thermoelectric effect
Ans: C
103. The magnetic material used in audio transformers is
A) Silicon steel
B) Cast iron
C) Nickel
D) Ferrite
Ans: A
104. Copper and silver are good conductors because
A) They have more protons
B) They have free electrons
C) They are non-magnetic
D) They are crystalline
Ans: B
105. The value of resistivity of copper at 20°C is approximately
A) Ω·m
B) Ω·m
C) Ω·m
D) Ω·m
Ans: A
106. The alloy used for heating element is
A) Brass
B) Nichrome
C) Duralumin
D) Phosphor bronze
Ans: B
107. The magnetic flux in a material is directly proportional to
A) Magnetizing force
B) Magnetic field strength
C) Permeability
D) All of these
Ans: D
108. The magnetic domains are present in
A) Ferromagnetic materials
B) Diamagnetic materials
C) Paramagnetic materials
D) All of these
Ans: A
109. The process of increasing the permeability and reducing hysteresis loss in magnetic material is
A) Hardening
B) Annealing
C) Tempering
D) None
Ans: B
110. The best insulator among the following is
A) Rubber
B) Mica
C) Paper
D) Glass
Ans: D
111. In an intrinsic semiconductor, the number of electrons is equal to
A) Number of protons
B) Number of holes
C) Number of donors
D) None
Ans: B
112. The common insulating material in underground cables is
A) PVC
B) Paper
C) Rubber
D) All of these
Ans: D
113. The magnetic materials are classified based on
A) Magnetic susceptibility
B) Magnetic flux
C) Electric field
D) Hysteresis loss
Ans: A
114. The Curie temperature for iron is approximately
A) 200°C
B) 400°C
C) 770°C
D) 1000°C
Ans: C
115. The resistivity of carbon is
A) Very high
B) Very low
C) Medium
D) Negligible
Ans: C
116. The element commonly used for doping silicon to make it n-type is
A) Boron
B) Phosphorus
C) Indium
D) Gallium
Ans: B
117. The material having very low coercivity is suitable for
A) Permanent magnets
B) Electromagnets
C) Magnetic tapes
D) Loudspeakers
Ans: B
118. The dielectric loss in a material is measured by
A) Loss tangent (tan δ)
B) Hysteresis curve
C) Relative permittivity
D) Conductivity
Ans: A
119. In ferromagnetic materials, magnetic domains are
A) Randomly oriented
B) Aligned parallel
C) Opposite
D) Equal
Ans: A
120. Eddy current losses are minimized by
A) Using thick laminations
B) Using thin laminations
C) Using solid core
D) Increasing conductivity
Ans: B
121. The temperature coefficient of resistance for insulators is
A) Positive
B) Negative
C) Zero
D) None
Ans: B
122. In dielectrics, conduction takes place by
A) Free electrons
B) Ion migration
C) Both A and B
D) None
Ans: B
123. The capacitance of a capacitor increases with
A) Increase in area of plates
B) Decrease in plate separation
C) Use of higher permittivity dielectric
D) All of these
Ans: D
124. The dielectric constant of vacuum is
A) 1
B) 8.85 × 10⁻¹²
C) 0
D) Infinite
Ans: A
125. Permanent magnets should have
A) High retentivity and high coercivity
B) High permeability
C) Low hysteresis
D) Low resistivity
Ans: A
126. Which of the following is not a semiconductor material?
A) Silicon
B) Germanium
C) Selenium
D) Copper
Ans: D
127. Electrical conductivity is highest for
A) Aluminum
B) Copper
C) Silver
D) Gold
Ans: C
128. A good conductor should have
A) Low resistivity
B) High conductivity
C) High temperature coefficient
D) A and B
Ans: D
129. The term “ferromagnetism” is derived from
A) Ferrite
B) Iron (Ferrum)
C) Magnetic field
D) Ferroalloy
Ans: B
130. The relative permittivity of air is approximately
A) 0
B) 1
C) 5
D) 10
Ans: B
131. When current flows through a conductor, heat is produced due to
A) Induction
B) Resistance
C) Capacitance
D) Permeability
Ans: B
132. Pure silicon crystal is
A) Metallic conductor
B) Non-metallic insulator
C) Semiconductor
D) Magnetic
Ans: C
133. Doping concentration in semiconductors is typically
A) 10⁸ atoms/cm³
B) 10¹⁰ atoms/cm³
C) 10¹⁶ atoms/cm³
D) 10²⁴ atoms/cm³
Ans: C
134. The conduction in p-type semiconductor is due to
A) Electrons
B) Holes
C) Both A and B
D) None
Ans: B
135. Magnetostriction effect is used in
A) Transformers
B) Ultrasonic generators
C) Capacitors
D) Inductors
Ans: B
136. The thermal runaway in semiconductors occurs due to
A) Increase in mobility
B) Decrease in resistance with temperature
C) Increase in resistance
D) None
Ans: B
137. Conductivity of pure water is
A) Very high
B) Very low
C) Moderate
D) Infinite
Ans: B
138. Piezoelectric materials convert
A) Mechanical energy into electrical energy
B) Electrical energy into mechanical energy
C) Both A and B
D) None
Ans: C
139. Ferrites have
A) High resistivity and low eddy current loss
B) Low resistivity and high eddy current loss
C) High resistivity and high permeability
D) None
Ans: A
140. Thermoelectric effect is basis of
A) Thermocouples
B) Piezoelectric sensors
C) Capacitors
D) Relays
Ans: A
141. Which of the following has least resistivity at room temperature?
A) Copper
B) Silver
C) Aluminum
D) Gold
Ans: B
142. The best conductor of heat is
A) Silver
B) Copper
C) Aluminum
D) Iron
Ans: A
143. The energy stored in a magnetic field is proportional to
A) Flux
B) Flux²
C) Current
D) None
Ans: B
144. The dielectric strength of transformer oil is about
A) 5 kV/mm
B) 10 kV/mm
C) 15 kV/mm
D) 30 kV/mm
Ans: D
145. The saturation of magnetic material means
A) Maximum flux density reached
B) Minimum flux density
C) Hysteresis loop closed
D) Magnetization zero
Ans: A
146. B-H curve is steepest for
A) Soft iron
B) Hard steel
C) Nickel
D) Copper
Ans: A
147. The major impurity in aluminum is
A) Iron
B) Silicon
C) Copper
D) Carbon
Ans: B
148. The hysteresis loss per unit volume is proportional to
A) Frequency
B) Flux density
C) Area of hysteresis loop × frequency
D) Volume
Ans: C
149. Dielectric heating is used in
A) Transformers
B) Induction furnaces
C) Plastic welding
D) Magnetic relays
Ans: C
150. High resistivity alloys are used in
A) Heating elements
B) Transmission lines
C) Armature windings
D) Bus bars
Ans: A
151. Silicon steel contains about
A) 4% Si
B) 10% Si
C) 0.1% Si
D) 20% Si
Ans: A
152. The main cause of dielectric breakdown is
A) Excess voltage
B) Ionization
C) Heating
D) All of these
Ans: D
153. The resistance of copper wire increases when
A) Temperature decreases
B) Temperature increases
C) Length decreases
D) Cross-section increases
Ans: B
154. The current in a semiconductor is due to
A) Holes
B) Electrons
C) Both A and B
D) None
Ans: C
155. The main cause of eddy current loss is
A) Changing magnetic field
B) Static magnetic field
C) Constant current
D) Uniform flux
Ans: A
156. Paramagnetic materials are used in
A) Cores of inductors
B) None (rarely used)
C) Transformers
D) Motors
Ans: B
157. Resistance temperature detectors (RTDs) are made of
A) Copper
B) Platinum
C) Nickel
D) All of these
Ans: D
158. The ratio of electric flux density to electric field intensity is
A) Permittivity
B) Permeability
C) Reluctivity
D) Conductivity
Ans: A
159. The electron mobility in germanium compared to silicon is
A) Higher
B) Lower
C) Equal
D) None
Ans: A
160. The temperature coefficient of resistance for carbon is
A) Positive
B) Negative
C) Zero
D) Infinite
Ans: B
161. Which insulator has highest dielectric strength?
A) Air
B) Mica
C) Porcelain
D) Glass
Ans: D
162. The material used for high-frequency transformer cores is
A) Laminated steel
B) Ferrite
C) Cast iron
D) Copper
Ans: B
163. An ideal insulator should have
A) High resistivity
B) High dielectric strength
C) Low dielectric loss
D) All of these
Ans: D
164. The skin effect increases with
A) Frequency
B) Decrease in frequency
C) Decrease in resistivity
D) None
Ans: A
165. Which material has negative temperature coefficient of resistance?
A) Metal
B) Semiconductor
C) Alloy
D) Superconductor
Ans: B
166. The contact resistance of silver is
A) High
B) Low
C) Medium
D) Infinite
Ans: B
167. The resistivity of an alloy is
A) Lower than pure metal
B) Higher than pure metal
C) Equal to pure metal
D) Zero
Ans: B
168. The insulating material commonly used in transformers is
A) Porcelain
B) Transformer oil
C) Rubber
D) Air
Ans: B
169. The value of magnetic flux density in vacuum is
A) 0
B) μ₀H
C) 1
D) H
Ans: B
170. The material used in thermionic emission is
A) Tungsten
B) Copper
C) Iron
D) Mica
Ans: A
171. The temperature at which resistivity of a semiconductor becomes infinite is called
A) Freezing point
B) Critical temperature
C) Absolute zero
D) Curie temperature
Ans: C
172. The term “magnetization” refers to
A) Magnetic flux per unit area
B) Magnetic moment per unit volume
C) Total flux in coil
D) None
Ans: B
173. The magnetic flux density is given by
A) B = μH
B) B = H/μ
C) B = μ₀/μr
D) B = Hμ²
Ans: A
174. A semiconductor doped with trivalent impurity is
A) N-type
B) P-type
C) Intrinsic
D) None
Ans: B
175. The specific resistance is expressed in
A) Ω
B) Ω·m
C) mho
D) siemens
Ans: B
176. The saturation magnetization decreases with
A) Increase in temperature
B) Decrease in temperature
C) Constant temperature
D) None
Ans: A
177. The magnetization curve between B and H is
A) Linear
B) Non-linear
C) Exponential
D) Parabolic
Ans: B
178. The unit of reluctance is
A) Ampere-turn/Wb
B) H/m
C) Wb/m²
D) Tesla
Ans: A
179. The resistance of an ideal conductor is
A) Zero
B) Infinity
C) Constant
D) None
Ans: A
180. The property of a material by virtue of which it opposes magnetic flux is
A) Reluctance
B) Permeability
C) Magnetization
D) Conductivity
Ans: A
181. The process of magnetization is complete when
A) All domains are aligned
B) No domains exist
C) Magnetic flux is zero
D) Field is removed
Ans: A
182. The rate of energy dissipation in a resistor is
A) I²R
B) IR
C) VI²
D) V²/I
Ans: A
183. When two magnetic materials are in series, total reluctance is
A) Sum of individual reluctances
B) Product of individual reluctances
C) Ratio of individual reluctances
D) None
Ans: A
184. The energy stored per unit volume in magnetic field is
A) (1/2)BH
B) BH
C) B²/μ
D) μH²
Ans: A
185. The main use of manganin is in
A) Standard resistors
B) Heating elements
C) Transformer cores
D) Armature windings
Ans: A
186. The dielectric constant of mica is approximately
A) 2
B) 4
C) 6
D) 8
Ans: C
187. The resistivity of Nichrome is about
A) 1.1 × 10⁻⁶ Ω·m
B) 1.1 × 10⁻⁸ Ω·m
C) 1.1 × 10⁻⁴ Ω·m
D) 1.1 × 10⁻¹⁰ Ω·m
Ans: A
188. The coercivity of a soft magnetic material is
A) Low
B) High
C) Very high
D) Infinite
Ans: A
189. Which of the following materials exhibits superconductivity?
A) Mercury
B) Aluminum
C) Tin
D) All of these
Ans: D
190. The dielectric loss angle δ represents
A) Phase angle between current and voltage
B) Power factor of dielectric
C) Both A and B
D) None
Ans: C
191. The ability of material to allow magnetic flux is
A) Permeability
B) Permittivity
C) Conductivity
D) Susceptibility
Ans: A
192. In ferrimagnetic materials, magnetic moments are
A) Opposite and unequal
B) Opposite and equal
C) Parallel
D) Zero
Ans: A
193. Carbon resistors are generally
A) Wire-wound type
B) Fixed type
C) Variable type
D) Thin-film type
Ans: B
194. For minimum eddy current loss, material should have
A) Low conductivity and high resistivity
B) High conductivity
C) Low resistivity
D) None
Ans: A
195. The process of magnetizing a material permanently is called
A) Hardening
B) Annealing
C) Magnetization
D) Magnetizing
Ans: A
196. The energy stored in a capacitor is
A) (1/2)CV²
B) (1/2)QV
C) (1/2)Q²/C
D) All of these
Ans: D
197. The maximum energy stored in an inductor is
A) (1/2)LI²
B) LI
C) I²/L
D) L²I²
Ans: A
198. The electric field inside a perfect conductor is
A) Zero
B) Infinite
C) Finite
D) Constant
Ans: A
199. Superconductors have
A) Zero resistance
B) Infinite conductivity
C) Meissner effect
D) All of these
Ans: D
200. The most important property of dielectric material is
A) High permittivity and high dielectric strength
B) Low conductivity
C) Low resistivity
D) High hysteresis
Ans: A
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