Q41. The dielectric constant of porcelain is approximately:
A) 2
B) 3.8–6
C) 10–15
D) 20–25
Ans: B
Q42. The dielectric constant of glass used in insulators is around:
A) 2
B) 4–10
C) 12–20
D) 1
Ans: B
Q43. The electric field between two parallel conductors in air is:
A) Uniform
B) Non-uniform
C) Zero
D) Infinite
Ans: B
Q44. Electric field lines always originate from:
A) Positive charge
B) Negative charge
C) Ground
D) Neutral point
Ans: A
Q45. The electric potential decreases in the direction of:
A) Increasing electric field
B) Decreasing electric field
C) Perpendicular to electric field
D) None
Ans: A
Q46. The breakdown of an insulator due to localized heating is called:
A) Thermal breakdown
B) Avalanche breakdown
C) Corona
D) Ionization
Ans: A
Q47. The breakdown voltage of an insulator increases with:
A) Thickness
B) Temperature
C) Humidity
D) None
Ans: A
Q48. Dielectric strength of mica is around:
A) 20–30 kV/mm
B) 10–15 kV/mm
C) 3 kV/mm
D) 1 kV/mm
Ans: A
Q49. The main cause of dielectric breakdown in solids is:
A) Thermal effect
B) Electromechanical stress
C) Defects in material
D) All
Ans: D
Q50. Dielectric loss in an insulating material is mainly due to:
A) Polarization lag
B) High frequency
C) Leakage current
D) All
Ans: D
Q51. For a given conductor spacing, the electric field can be reduced by:
A) Increasing conductor diameter
B) Decreasing diameter
C) Increasing voltage
D) None
Ans: A
Q52. In high-voltage systems, corona occurs first at:
A) Points of maximum electric field
B) Points of minimum electric field
C) At uniform field
D) Nowhere
Ans: A
Q53. The potential at any point due to a point charge is proportional to:
A) 1/r
B) 1/r²
C) r
D) None
Ans: A
Q54. In air, the dielectric breakdown occurs when:
A) Electric stress > 30 kV/cm
B) Electric stress < 30 kV/cm
C) Uniform field exists
D) None
Ans: A
Q55. The potential distribution along suspension string is improved by:
A) Capacitive grading
B) Static shielding
C) Both
D) None
Ans: C
Q56. The voltage across top disc of a string is usually:
A) Least
B) Maximum
C) Equal
D) Zero
Ans: A
Q57. The electric stress at the conductor surface is proportional to:
A) Voltage / Radius
B) Voltage × Radius
C) Radius / Voltage
D) None
Ans: A
Q58. The electric field between concentric cylinders is:
A) Radial
B) Tangential
C) Axial
D) Uniform
Ans: A
Q59. The dielectric strength of a vacuum is approximately:
A) 30 kV/cm
B) 80–100 kV/cm
C) 10 kV/cm
D) 3 kV/cm
Ans: B
Q60. The function of arcing horns on an insulator is to:
A) Protect insulator from flashover
B) Increase voltage
C) Decrease leakage
D) Provide mechanical support
Ans: A
Q61. In polluted conditions, flashover occurs due to:
A) Surface conductivity
B) Air ionization
C) Internal defects
D) None
Ans: A
Q62. The electric field intensity (E) and potential (V) relation is:
A)
B)
C)
D) None
Ans: A
Q63. Field lines never intersect because:
A) There is only one direction of field at a point
B) Field is discontinuous
C) Charges repel
D) None
Ans: A
Q64. Equipotential surfaces are always:
A) Perpendicular to electric field lines
B) Parallel to field lines
C) Tangent to field lines
D) Random
Ans: A
Q65. The dielectric loss angle (δ) is small for:
A) Good insulators
B) Poor insulators
C) Conductors
D) All materials
Ans: A
Q66. A good insulator has:
A) High resistivity, low loss angle
B) Low resistivity, high loss angle
C) High conductivity
D) None
Ans: A
Q67. The electric flux density (D) is related to E as:
A) D = εE
B) D = E/ε
C) D = ε/E
D) D = E²
Ans: A
Q68. The permittivity of free space (ε₀) is:
A) 8.854 × 10⁻¹² F/m
B) 8.854 × 10⁻⁹ F/m
C) 10⁻⁶ F/m
D) 1 F/m
Ans: A
Q69. The relative permittivity of air is approximately:
A) 1
B) 2
C) 3
D) 10
Ans: A
Q70. The line capacitance of transmission lines is due to:
A) Electric field between conductors
B) Magnetic field
C) Resistance
D) Inductance
Ans: A
Q71. Grading of cables and insulators is used to:
A) Equalize potential
B) Reduce stress at high-voltage points
C) Prevent breakdown
D) All
Ans: D
Q72. The surface of a charged conductor in electrostatic equilibrium is:
A) Equipotential
B) Non-uniform
C) Varying with charge
D) None
Ans: A
Q73. Electric field inside a perfect conductor is:
A) Zero
B) Finite
C) Maximum
D) Infinite
Ans: A
Q74. When two dielectrics are in series, the electric displacement D is:
A) Same in both
B) Different in both
C) Zero
D) None
Ans: A
Q75. The unit of electric flux density (D) is:
A) C/m²
B) V/m
C) N/C
D) J/C
Ans: A
Q76. Potential distribution across insulators is analyzed using:
A) Capacitance model
B) Resistance model
C) Both
D) None
Ans: C
Q77. Surface discharges on insulators are also called:
A) Tracking
B) Flashover
C) Breakdown
D) Arcing
Ans: A
Q78. Insulator resistance decreases with:
A) Temperature rise
B) Humidity
C) Both
D) None
Ans: C
Q79. In composite insulators, the core is usually made of:
A) Fiberglass reinforced plastic
B) Porcelain
C) Metal
D) Silicone rubber
Ans: A
Q80. The field distribution in multi-dielectric systems depends on:
A) Permittivity ratio
B) Voltage
C) Frequency
D) None
Ans: A
Q81. Leakage current in insulators mainly flows:
A) Over the surface
B) Through the body
C) Through the metal fittings
D) Through air
Ans: A
Q82. The purpose of increasing creepage distance is to:
A) Avoid surface flashover
B) Increase insulation
C) Prevent leakage current
D) All
Ans: D
Q83. The potential distribution along insulator discs becomes more uniform with:
A) More grading rings
B) Less capacitance to earth
C) Both
D) None
Ans: C
Q84. The voltage stress across each disc in a string without grading is:
A) Unequal
B) Equal
C) Zero
D) None
Ans: A
Q85. For a single disc insulator, string efficiency is:
A) 100%
B) 90%
C) 70%
D) 50%
Ans: A
Q86. Porcelain insulators are made by mixing:
A) Clay, quartz, feldspar
B) Cement and silica
C) Glass and metal
D) None
Ans: A
Q87. Glass insulators are preferred because of:
A) Transparency and self-cleaning
B) Cheapness
C) Strength
D) None
Ans: A
Q88. The electric field inside a dielectric is less than in air due to:
A) Polarization
B) Leakage
C) Resistance
D) None
Ans: A
Q89. When the potential gradient exceeds dielectric strength, what occurs?
A) Breakdown
B) Corona
C) Flashover
D) Tracking
Ans: A
Q90. Dry bands on insulators occur due to:
A) Partial drying under leakage current
B) Voltage variation
C) Wind pressure
D) None
Ans: A
Q91. Dry band arcing can lead to:
A) Flashover
B) Breakdown
C) Tracking
D) All
Ans: D
Q92. The field intensity near a sharp point is:
A) High
B) Low
C) Zero
D) Constant
Ans: A
Q93. Field mapping is done to:
A) Study equipotential lines
B) Find electric field strength
C) Visualize field distribution
D) All
Ans: D
Q94. The total charge enclosed by a Gaussian surface is given by:
A) Gauss’s Law
B) Coulomb’s Law
C) Ohm’s Law
D) Faraday’s Law
Ans: A
Q95. The electric flux through a closed surface depends on:
A) Net charge enclosed
B) Surface area
C) Medium permittivity
D) Both A & C
Ans: D
Q96. The potential distribution of an insulator string depends on:
A) Capacitance ratio
B) Leakage resistance
C) Both
D) None
Ans: C
Q97. The electric stress at line end of an insulator is highest due to:
A) Concentrated capacitance to earth
B) Corona
C) Leakage current
D) None
Ans: A
Q98. To improve voltage distribution, the lower discs of the string should have:
A) Higher capacitance
B) Lower capacitance
C) Equal capacitance
D) None
Ans: A
Q99. The main factor affecting flashover voltage is:
A) Pollution level
B) Frequency
C) Temperature
D) Altitude
Ans: A
Q100. String efficiency can be improved by:
A) Grading rings
B) Increasing mutual capacitance
C) Both A & B
D) None
Ans: C
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