Q.1 What is an insulator in electrical terms?
A material that allows electricity to flow easily
A material that blocks or limits the flow of electricity
A device that stores electrical energy
A conductor with high resistance
Explanation - Insulators are materials that resist the flow of electric current, thereby preventing electrical conduction.
Correct answer is: A material that blocks or limits the flow of electricity
Q.2 Which of the following is commonly used as an insulator in household wires?
Copper
Aluminum
PVC
Steel
Explanation - PVC (polyvinyl chloride) is a plastic used as insulation around wires because it resists electrical conduction.
Correct answer is: PVC
Q.3 Why do glass bottles resist electricity?
Because they are metals
Because they have a high melting point
Because they are non-conductive materials
Because they conduct heat well
Explanation - Glass is a non-conductive material, meaning it does not allow electrons to move freely, so it resists electric flow.
Correct answer is: Because they are non-conductive materials
Q.4 What property of a material determines its ability to resist electric current?
Hardness
Color
Resistance
Weight
Explanation - Electrical resistance is the measure of how strongly a material opposes the flow of electric current.
Correct answer is: Resistance
Q.5 Which of these materials is NOT an insulator?
Rubber
Water
Aluminum
Ceramic
Explanation - Aluminum is a metal and a good conductor, not an insulator.
Correct answer is: Aluminum
Q.6 Why do we use rubber gloves when working with electricity?
Because rubber is a conductor
Because rubber can be stretched
Because rubber is an insulator
Because rubber conducts heat
Explanation - Rubber blocks the flow of electric current, protecting the wearer from electrical shock.
Correct answer is: Because rubber is an insulator
Q.7 What is the main advantage of using silicone as insulation for cables?
It conducts electricity well
It has a low melting point
It is flexible and resistant to heat
It is very expensive
Explanation - Silicone rubber remains flexible at high temperatures and does not conduct electricity, making it good for cable insulation.
Correct answer is: It is flexible and resistant to heat
Q.8 Which of the following is a high‑strength insulator used in high‑voltage power lines?
Fiberglass
Plastic
Steel
Wood
Explanation - Fiberglass (glass fiber) has excellent dielectric strength and is widely used in high‑voltage insulators.
Correct answer is: Fiberglass
Q.9 If a material has a high dielectric constant, what does it mean?
It conducts electricity easily
It stores more electric charge
It melts easily
It is magnetic
Explanation - A high dielectric constant indicates the material can hold more electric field and store charge in a capacitor.
Correct answer is: It stores more electric charge
Q.10 Which insulator would you NOT use for a transformer winding?
Oil
Paper
PVC
Silicone
Explanation - Oil is a liquid and would conduct electricity, which is undesirable in a transformer winding.
Correct answer is: Oil
Q.11 Why are ceramic materials often used in capacitors?
They are cheap
They conduct electricity well
They have a high dielectric strength
They melt easily
Explanation - Ceramic insulators can withstand high electric fields without breaking down, ideal for capacitors.
Correct answer is: They have a high dielectric strength
Q.12 What effect does moisture have on an insulator?
It improves conductivity
It has no effect
It reduces resistance
It makes it harder
Explanation - Moisture can increase the conductivity of an insulator, making it less effective.
Correct answer is: It reduces resistance
Q.13 Which is a property of a good electrical insulator?
High electrical conductivity
Low dielectric loss
Low melting point
High thermal expansion
Explanation - Low dielectric loss means the insulator does not dissipate much electrical energy as heat.
Correct answer is: Low dielectric loss
Q.14 What is dielectric breakdown?
When a material becomes a better conductor
When a material stops insulating and starts conducting
When a material melts
When a material expands
Explanation - Dielectric breakdown occurs when the electric field exceeds a material’s capacity, causing it to conduct electricity.
Correct answer is: When a material stops insulating and starts conducting
Q.15 Which insulator is known for its very low dielectric loss?
Glass
Plastic
Paper
Steel
Explanation - Glass has a very low dielectric loss, making it suitable for high‑frequency applications.
Correct answer is: Glass
Q.16 Why is Teflon used in high‑temperature electrical insulation?
It is cheap
It is a good conductor
It has high temperature resistance and low dielectric loss
It is magnetic
Explanation - Teflon (PTFE) can withstand high temperatures and does not lose much energy to heat.
Correct answer is: It has high temperature resistance and low dielectric loss
Q.17 What does the term 'surface resistivity' refer to?
Resistance of a material’s interior
Resistance of a material’s surface to electric current
Thickness of the insulation
Speed of electrical conduction
Explanation - Surface resistivity measures how well a material resists current flow along its surface.
Correct answer is: Resistance of a material’s surface to electric current
Q.18 Which material is commonly used as a dielectric in high‑frequency circuits?
Ceramic
Steel
Copper
Aluminum
Explanation - Ceramic dielectrics have low loss and stable properties at high frequencies.
Correct answer is: Ceramic
Q.19 How does temperature affect the resistivity of a plastic insulator?
It decreases with increasing temperature
It increases with increasing temperature
It stays the same
It becomes zero
Explanation - Plastic insulators usually become less conductive (higher resistivity) as temperature rises.
Correct answer is: It increases with increasing temperature
Q.20 Which is a key benefit of using polymer insulators in cables?
They conduct electricity well
They are heavy and rigid
They are flexible and lightweight
They melt easily
Explanation - Polymers are light, flexible, and provide good insulation for cables.
Correct answer is: They are flexible and lightweight
Q.21 What is the primary reason for using ceramic insulators on high‑voltage power lines?
They are cheap
They can withstand high electric fields
They conduct electricity
They are magnetic
Explanation - Ceramic insulators have high dielectric strength, making them ideal for high‑voltage transmission.
Correct answer is: They can withstand high electric fields
Q.22 Which insulator would be best for an environment with high humidity?
Water
Glass
Paper
Oil
Explanation - Glass is unaffected by moisture and remains a good insulator even in humid conditions.
Correct answer is: Glass
Q.23 What is a common application of a polymer insulator?
Power transmission lines
Electric motors
Capacitors
Copper wires
Explanation - Polymers are often used as dielectric materials in capacitor construction.
Correct answer is: Capacitors
Q.24 Which factor does NOT affect the dielectric strength of an insulator?
Thickness of the material
Purity of the material
Temperature
Color of the material
Explanation - Dielectric strength depends on thickness, purity, and temperature, but not on color.
Correct answer is: Color of the material
Q.25 Why are epoxy resins used in PCB insulation?
They are magnetic
They have high dielectric strength and good adhesion
They conduct electricity
They are very flexible
Explanation - Epoxy resins bond well to copper and provide strong electrical insulation.
Correct answer is: They have high dielectric strength and good adhesion
Q.26 Which insulator would be most suitable for a high‑frequency RF amplifier?
Glass
Plastic
Paper
Steel
Explanation - Glass has low dielectric loss, which is critical for RF applications.
Correct answer is: Glass
Q.27 What does 'dielectric constant' describe?
The mechanical strength of a material
The amount of heat a material can absorb
The ability of a material to store electric energy
The magnetic permeability of a material
Explanation - The dielectric constant indicates how much electric field a material can store per unit volume.
Correct answer is: The ability of a material to store electric energy
Q.28 Which material is typically used as a high‑temperature insulator for transformer oil?
Silicone rubber
PVC
Paper
Aluminum
Explanation - Silicone rubber can withstand transformer oil temperatures and remains insulating.
Correct answer is: Silicone rubber
Q.29 Which property is crucial for an insulator used in a high‑voltage substation?
High electrical conductivity
High dielectric loss
High dielectric strength
Low melting point
Explanation - Insulators in substations must resist very high electric fields without breaking down.
Correct answer is: High dielectric strength
Q.30 What is the main disadvantage of using paper as insulation in power cables?
It is too expensive
It degrades with moisture and heat
It conducts electricity
It is very flexible
Explanation - Paper insulators can absorb moisture and degrade under heat, reducing their effectiveness.
Correct answer is: It degrades with moisture and heat
Q.31 Which insulator material is known for its very low dielectric loss at microwave frequencies?
Ceramic
PVC
Silicone rubber
Paper
Explanation - Ceramics have minimal dielectric loss, making them ideal for microwave components.
Correct answer is: Ceramic
Q.32 Which insulator is commonly used in the interior of power transformers?
Silicone rubber
Glass
Aluminum
Steel
Explanation - Silicone rubber insulates windings while tolerating the high temperatures of transformers.
Correct answer is: Silicone rubber
Q.33 Why is Teflon often used in high‑frequency circuit boards?
It is inexpensive
It has high dielectric constant
It has low dielectric loss
It is magnetic
Explanation - Teflon (PTFE) maintains low loss at high frequencies, preserving signal integrity.
Correct answer is: It has low dielectric loss
Q.34 What is the primary function of a dielectric in a capacitor?
Conduct electricity
Store charge
Generate magnetic fields
Serve as a conductor
Explanation - The dielectric prevents charge flow between plates while storing electric energy.
Correct answer is: Store charge
Q.35 Which of these is a characteristic of a polymer insulator?
High thermal conductivity
Low flexibility
High dielectric strength
High dielectric loss
Explanation - Polymers provide good electrical insulation and can handle high voltage levels.
Correct answer is: High dielectric strength
Q.36 Which material would be best to insulate a high‑voltage cable in a humid environment?
PVC
Paper
Silicone rubber
Steel
Explanation - Silicone rubber resists moisture absorption and maintains insulating properties.
Correct answer is: Silicone rubber
Q.37 What does 'dielectric loss' refer to in insulation materials?
Loss of mechanical strength
Heat generated due to electrical energy dissipation
Weight loss at high temperatures
Electrical conductivity increase
Explanation - Dielectric loss is the amount of electrical energy lost as heat within an insulator.
Correct answer is: Heat generated due to electrical energy dissipation
Q.38 Which insulator type has the highest dielectric strength per unit weight?
Ceramic
Glass
Polymers
Paper
Explanation - Ceramics offer the highest dielectric strength relative to their mass.
Correct answer is: Ceramic
Q.39 Why is mica considered an excellent insulator for transformers?
It is magnetic
It has high dielectric strength and good thermal stability
It is cheap
It conducts electricity
Explanation - Mica can withstand high voltages and temperatures, making it ideal for transformer cores and insulation.
Correct answer is: It has high dielectric strength and good thermal stability
Q.40 Which insulator material is most commonly used for the outer sheath of power cables?
PVC
Paper
Steel
Ceramic
Explanation - PVC is flexible, inexpensive, and provides adequate insulation for many power cables.
Correct answer is: PVC
Q.41 What is the primary advantage of using a cross‑linked polyethylene (XLPE) insulator?
It is cheaper than PVC
It can handle higher temperatures and voltages
It has higher dielectric loss
It melts easily
Explanation - XLPE offers better thermal and electrical performance than conventional polyethylene.
Correct answer is: It can handle higher temperatures and voltages
Q.42 Which insulator has a dielectric constant between 2.2 and 2.5?
PTFE
PVC
Silicone rubber
Paper
Explanation - PVC’s dielectric constant typically falls in the 2.2–2.5 range.
Correct answer is: PVC
Q.43 Why do transformer insulators often contain a blend of cellulose and polymer?
To reduce cost
To improve mechanical strength and electrical performance
To increase conductivity
To increase weight
Explanation - The blend offers both good insulation and mechanical durability.
Correct answer is: To improve mechanical strength and electrical performance
Q.44 Which insulator material is most suitable for use in high‑frequency RF feedlines?
Ceramic
PVC
Silicone rubber
Paper
Explanation - Ceramic dielectrics have low dielectric loss at high frequencies.
Correct answer is: Ceramic
Q.45 What does 'surface resistivity' affect in high‑voltage equipment?
Conduction through the interior
Leakage current along the surface
Magnetic field strength
Thermal expansion
Explanation - High surface resistivity reduces surface leakage currents, improving insulation safety.
Correct answer is: Leakage current along the surface
Q.46 Which type of insulation material is typically used in high‑temperature cables for power transmission?
XLPE
PVC
Paper
Steel
Explanation - XLPE can withstand higher temperatures than PVC, making it suitable for hot environments.
Correct answer is: XLPE
Q.47 Which insulator provides the lowest dielectric loss at gigahertz frequencies?
PTFE (Teflon)
PVC
Silicone rubber
Paper
Explanation - PTFE has exceptionally low loss tangent at gigahertz frequencies.
Correct answer is: PTFE (Teflon)
Q.48 What is the main reason for using a water‑based dielectric fluid in high‑voltage transformers?
It conducts electricity well
It provides excellent cooling and dielectric properties
It is inexpensive
It increases magnetic flux
Explanation - Water cools the transformer while also acting as a dielectric to insulate windings.
Correct answer is: It provides excellent cooling and dielectric properties
Q.49 Which insulator type is most likely to experience partial discharge?
Solid ceramic
Solid polymer
Wet paper
Metal
Explanation - Moisture in paper can lead to partial discharge, a localized ionization event.
Correct answer is: Wet paper
Q.50 Which property of an insulating material is most critical for high‑voltage applications?
Dielectric strength
Thermal conductivity
Optical clarity
Magnetic permeability
Explanation - High dielectric strength prevents electric breakdown in high‑voltage systems.
Correct answer is: Dielectric strength
Q.51 Which insulating material is preferred for use in high‑temperature gas‑insulated switchgear?
Ceramic
Polymer
Paper
Glass
Explanation - Ceramic can handle the high temperatures and electrical stresses of gas‑insulated switchgear.
Correct answer is: Ceramic
Q.52 Which insulator would you use to insulate a high‑voltage DC cable?
PVC
XLPE
Silicone rubber
Paper
Explanation - XLPE has low dielectric loss and can handle high DC voltages.
Correct answer is: XLPE
Q.53 What is a primary concern when selecting an insulator for a high‑power transmission line?
Color of the material
Dielectric strength and mechanical robustness
Cost of the material only
Electrical conductivity
Explanation - Both electrical and mechanical properties must be high for safe operation.
Correct answer is: Dielectric strength and mechanical robustness
Q.54 Which insulator material has the highest thermal conductivity?
Glass
Ceramic
Silicone rubber
Paper
Explanation - Ceramics like alumina have high thermal conductivity, which can help dissipate heat.
Correct answer is: Ceramic
Q.55 Why is silicone rubber preferred for underground cable insulation?
It is magnetic
It has high water absorption
It is flexible and resistant to moisture
It conducts electricity
Explanation - Silicone rubber resists water and can flex during underground installation.
Correct answer is: It is flexible and resistant to moisture
Q.56 Which material is typically used for the dielectric in high‑frequency PCB traces?
FR‑4 (epoxy resin)
PVC
Silicone rubber
Paper
Explanation - FR‑4 provides good dielectric performance and mechanical strength for PCB substrates.
Correct answer is: FR‑4 (epoxy resin)
Q.57 What is the typical dielectric constant of polyethylene (PE)?
1.0–1.5
2.2–2.5
4.5–5.0
10.0–12.0
Explanation - Polyethylene has a low dielectric constant, typically around 1.0 to 1.5.
Correct answer is: 1.0–1.5
Q.58 Which insulator is most suitable for use in cryogenic environments?
Silicone rubber
Polyethylene
Mica
PVC
Explanation - Mica maintains its insulating properties even at very low temperatures.
Correct answer is: Mica
Q.59 Which type of insulation material is commonly used in high‑current power cables?
Paper
XLPE
PVC
Glass
Explanation - XLPE provides high current carrying capacity and excellent insulation.
Correct answer is: XLPE
Q.60 What is the main benefit of using a polymer composite as cable insulation?
Higher dielectric loss
Lower dielectric strength
Improved mechanical strength and dielectric performance
Higher cost
Explanation - Polymer composites combine the strengths of polymers and fillers for better performance.
Correct answer is: Improved mechanical strength and dielectric performance
Q.61 Which insulating material is known for its excellent high‑frequency performance and low loss tangent?
PTFE (Teflon)
PVC
Paper
Silicone rubber
Explanation - Teflon exhibits low loss tangent at high frequencies, making it ideal for RF components.
Correct answer is: PTFE (Teflon)
Q.62 Why are ceramic insulators preferred in high‑voltage insulator towers?
They conduct electricity
They have high dielectric strength and are resistant to weathering
They are inexpensive
They melt easily
Explanation - Ceramic insulators can withstand high voltages and harsh environmental conditions.
Correct answer is: They have high dielectric strength and are resistant to weathering
Q.63 Which insulator material is commonly used for the outer sheath of high‑voltage underground cables?
XLPE
PVC
Silicone rubber
Paper
Explanation - XLPE offers high voltage capability, flexibility, and durability for underground cables.
Correct answer is: XLPE
Q.64 Which of the following is NOT a typical property of good insulation material?
High dielectric strength
Low dielectric loss
High electrical conductivity
Low moisture absorption
Explanation - Good insulators have low conductivity; high conductivity is a characteristic of conductors.
Correct answer is: High electrical conductivity
Q.65 What is the primary effect of increasing temperature on the dielectric constant of polymer insulators?
It decreases the dielectric constant
It increases the dielectric constant
It has no effect
It causes the material to melt
Explanation - Polymers typically exhibit higher dielectric constants at elevated temperatures.
Correct answer is: It increases the dielectric constant
Q.66 Which material has the best combination of dielectric strength and thermal conductivity for transformer insulators?
Glass
Ceramic
Polyethylene
Paper
Explanation - Ceramic offers high dielectric strength and relatively good thermal conductivity for transformers.
Correct answer is: Ceramic
Q.67 Which insulator is most commonly used in high‑speed data cables?
PVC
Silicone rubber
PTFE
Paper
Explanation - PTFE provides low loss and high dielectric strength for high‑speed data transmission.
Correct answer is: PTFE
Q.68 What does 'partial discharge' refer to in electrical insulation?
A complete breakdown of the insulator
Localized ionization events inside the insulating material
The entire insulator melting
The insulator becoming conductive
Explanation - Partial discharge is a localized electrical discharge that can degrade insulation over time.
Correct answer is: Localized ionization events inside the insulating material
Q.69 Which of the following is a major advantage of using silicone rubber as cable insulation?
It conducts electricity
It has excellent moisture resistance
It has low dielectric strength
It melts at low temperatures
Explanation - Silicone rubber resists moisture, making it suitable for outdoor and underground cables.
Correct answer is: It has excellent moisture resistance
Q.70 Which material is commonly used for the dielectric in power transformer cores?
Silicone rubber
Mica
PVC
Paper
Explanation - Mica provides excellent dielectric properties and high-temperature stability for transformer cores.
Correct answer is: Mica
Q.71 Which insulator offers the lowest dielectric loss at microwave frequencies?
Ceramic
Silicone rubber
Paper
PVC
Explanation - Ceramic dielectrics exhibit minimal loss at microwave frequencies.
Correct answer is: Ceramic
Q.72 What is the primary benefit of using epoxy resin in PCBs?
High dielectric loss
Low dielectric constant
Excellent electrical insulation and mechanical strength
High magnetic permeability
Explanation - Epoxy resin provides robust electrical insulation and structural support for PCBs.
Correct answer is: Excellent electrical insulation and mechanical strength
Q.73 Which insulator would be chosen for a high‑temperature gas‑insulated switchgear?
Ceramic
PVC
Paper
Steel
Explanation - Ceramic insulators can withstand high temperatures and the dielectric requirements of switchgear.
Correct answer is: Ceramic
Q.74 Which property is most critical for a cable insulation material in high‑power applications?
Dielectric strength
Color
Magnetic permeability
Electrical conductivity
Explanation - High dielectric strength prevents breakdown under the large electric fields in high‑power systems.
Correct answer is: Dielectric strength
Q.75 Which insulator material is preferred for use in high‑frequency transmission lines?
Ceramic
PVC
Silicone rubber
Paper
Explanation - Ceramics have low dielectric loss and stable performance at high frequencies.
Correct answer is: Ceramic
Q.76 Which insulator provides excellent thermal stability and low dielectric loss for power cables?
XLPE
PVC
Paper
Steel
Explanation - XLPE is a cross‑linked polyethylene that offers high thermal stability and low dielectric loss.
Correct answer is: XLPE
Q.77 Why is Teflon used in high‑frequency PCB traces?
It is magnetic
It provides high dielectric loss
It offers low dielectric loss and high temperature stability
It conducts electricity
Explanation - Teflon’s low loss tangent is ideal for high‑frequency signal integrity.
Correct answer is: It offers low dielectric loss and high temperature stability
Q.78 What is the primary disadvantage of using paper as insulation in high‑voltage cables?
It absorbs moisture and ages
It is too expensive
It is magnetic
It conducts electricity
Explanation - Paper can absorb water and degrade over time, reducing its insulating properties.
Correct answer is: It absorbs moisture and ages
Q.79 Which insulator material is best suited for use in high‑temperature windings of a transformer?
Silicone rubber
Paper
PVC
Metal
Explanation - Silicone rubber can withstand high temperatures while providing excellent insulation.
Correct answer is: Silicone rubber
Q.80 Which of the following insulators has the lowest dielectric loss at 10 GHz?
PTFE
PVC
Paper
Silicone rubber
Explanation - PTFE exhibits very low dielectric loss at microwave frequencies.
Correct answer is: PTFE
Q.81 What is the main reason for using epoxy-based composites in high‑power electronics?
High electrical conductivity
Low dielectric constant
Good insulation and mechanical stability
Low cost
Explanation - Epoxy composites provide strong insulation and structural support for high‑power components.
Correct answer is: Good insulation and mechanical stability
Q.82 Which insulator material is known for its excellent dielectric performance and chemical resistance?
Ceramic
PVC
Paper
Silicone rubber
Explanation - Ceramic insulators resist chemical attack and maintain dielectric integrity.
Correct answer is: Ceramic
Q.83 Which insulator is commonly used in the dielectric of a high‑voltage capacitor?
Mica
Silicone rubber
PVC
Paper
Explanation - Mica offers high dielectric strength and temperature stability for capacitors.
Correct answer is: Mica
Q.84 Which material is preferred for the dielectric in a high‑frequency filter?
Ceramic
PVC
Paper
Metal
Explanation - Ceramic dielectrics provide low loss and stable performance at high frequencies.
Correct answer is: Ceramic
Q.85 What is a key advantage of using a composite of glass fiber and epoxy in cable insulation?
Higher dielectric loss
Improved mechanical strength and thermal stability
Lower dielectric constant
Higher electrical conductivity
Explanation - Glass fiber reinforcement enhances mechanical and thermal performance while maintaining insulation.
Correct answer is: Improved mechanical strength and thermal stability
Q.86 Which insulator material is best suited for use in ultra‑high voltage (UHV) power lines?
Ceramic
PVC
Silicone rubber
Paper
Explanation - Ceramics provide the high dielectric strength required for UHV applications.
Correct answer is: Ceramic
Q.87 What does the term 'loss tangent' refer to in dielectric materials?
The amount of mechanical loss
The ratio of dielectric loss to stored energy
The electrical conductivity
The thermal expansion coefficient
Explanation - Loss tangent (tan δ) measures how much energy is lost as heat compared to the energy stored in a dielectric.
Correct answer is: The ratio of dielectric loss to stored energy
Q.88 Which insulating material is commonly used in the construction of high‑temperature reactors?
Ceramic
PVC
Paper
Silicone rubber
Explanation - Ceramics can withstand extreme temperatures and electrical stresses in reactors.
Correct answer is: Ceramic
Q.89 Which insulator material provides the best combination of high dielectric strength and low moisture absorption for outdoor use?
Mica
Silicone rubber
PVC
Paper
Explanation - Mica resists moisture absorption while maintaining high dielectric strength.
Correct answer is: Mica
Q.90 Which insulator is most appropriate for use in high‑temperature gas‑insulated substations?
Ceramic
PVC
Silicone rubber
Paper
Explanation - Ceramic materials can endure the high temperatures and electric fields in gas‑insulated substations.
Correct answer is: Ceramic
Q.91 Why is Teflon used in the dielectric of high‑frequency microwave waveguides?
It provides high dielectric loss
It is magnetic
It offers very low loss and stable dielectric properties at high frequencies
It conducts electricity
Explanation - Teflon’s low loss tangent makes it ideal for microwave waveguides.
Correct answer is: It offers very low loss and stable dielectric properties at high frequencies
Q.92 Which insulator has the highest dielectric strength among common polymers?
Silicone rubber
Epoxy resin
PVC
XLPE
Explanation - XLPE exhibits high dielectric strength due to cross‑linking, making it suitable for high‑voltage applications.
Correct answer is: XLPE
Q.93 What is the main disadvantage of using paper as insulation in power cables?
High cost
Moisture absorption and aging
High dielectric loss
Low dielectric strength
Explanation - Paper can absorb water over time, which reduces its insulating properties.
Correct answer is: Moisture absorption and aging
Q.94 Which insulator material is best suited for use in the dielectric of a high‑temperature transformer core?
Silicone rubber
Mica
PVC
Paper
Explanation - Mica provides high dielectric strength and excellent temperature stability for transformer cores.
Correct answer is: Mica
Q.95 Which insulator is commonly used in the dielectric of an ultra‑high frequency (UHF) transmission line?
Ceramic
PVC
Silicone rubber
Paper
Explanation - Ceramic dielectrics offer low loss and high frequency performance for UHF lines.
Correct answer is: Ceramic
Q.96 What is the primary function of a dielectric material in an electrical capacitor?
To conduct electricity
To store electric energy by preventing charge flow between plates
To generate magnetic fields
To increase capacitance by adding more mass
Explanation - The dielectric insulates the plates, allowing the capacitor to store charge.
Correct answer is: To store electric energy by preventing charge flow between plates
Q.97 Which insulator material is used in the construction of high‑temperature gas‑insulated switchgear?
Ceramic
PVC
Paper
Metal
Explanation - Ceramic insulators can tolerate the high temperatures and electric fields in gas‑insulated switchgear.
Correct answer is: Ceramic
Q.98 Which insulator offers the lowest dielectric loss at terahertz frequencies?
PTFE
PVC
Silicone rubber
Paper
Explanation - PTFE remains low loss even at terahertz frequencies, suitable for advanced communication systems.
Correct answer is: PTFE