Free Wiring, Installation and Safety MCQs with Answers

• A. surface is moistened
• B. conductive dressing is done
• C. oil compound dressing is done
• D. talcum powder is sprayed on the surface

Explanation: A conductive dressing gives rubber or leather a slightly conductive surface so charges can leak away instead of accumulating.

• A. increases with rise in temperature
• B. increases with moisture content
• C. is same for all insulating materials
• D. none of the above

Explanation: Dielectric strength generally decreases as temperature or moisture increases, and it is different for different insulating materials.

• A. It will become magnetic
• B. It will melt
• C. It will get punctured or cracked
• D. Its molecular structure will get changed

Explanation: Applying a voltage above breakdown strength causes dielectric breakdown, which may puncture, crack, or otherwise permanently damage the…

• A. capacitor in parallel with contacts
• B. capacitor in series with each contact
• C. resistance in line
• D. none of the above

Explanation: A capacitor connected across the contacts provides a path for the sudden transient current and reduces the voltage rise that produces an…

• A. amount of moisture
• B. type of metals
• C. type of soil chemicals
• D. all above factors

Explanation: Underground corrosion is governed by moisture, the metals involved, and chemical composition of the surrounding soil.

• A. thin aluminium wires
• B. thin copper wires
• C. rigid cables
• D. flexible cables

Explanation: Vehicle battery connections must tolerate engine vibration and movement, so they are made with flexible cables rather than rigid…

• A. goggles or other face shield
• B. rubber
• C. rubber boots and gloves
• D. all above safety devices

Explanation: Electrolyte, especially sulphuric acid, can seriously injure the eyes and skin, so face protection, rubber gloves and rubber boots are…

• A. the increase in length of the insulation
• B. the decrease in the length of the insulation
• C. either A. or (b)
• D. none of the above

Explanation: Insulation resistance is proportional to cable length, as given by R = ρl/A.

• A. Polyvinyle chloride
• B. Vulcanised rubber
• C. Impregnated paper
• D. Compressed SFe gas
• E. none of the above

Explanation: At extremely high voltages, compressed SF6 gas is preferred in gas-insulated cable systems because its high dielectric strength permits…

• A. easy maintenance
• B. low cost
• C. can be used in congested areas
• D. can be used in high voltage circuits

Explanation: Underground cables require no overhead clearance and can be routed beneath streets, buildings and other congested locations.

• A. same at the conductor and the sheath
• B. minimum at the conductor and maximum at the sheath
• C. maximum at the conductor and minimum at the sheath
• D. zero at the conductor as well as on the sheath
• E. none of the above

Explanation: In a coaxial cable, electric stress is inversely proportional to the radius.

• A. to minimise temperature stresses
• B. to avoid being unearthed easily due to removal of soil
• C. to minimize the effect of shocks and vibrations due to gassing vehicles, etc
• D. for all of the above reasons

Explanation: The principal reason for laying cables at sufficient depth is to protect them from shocks, vibrations and mechanical damage caused by road…

• A. 0.04 mm
• B. 0.2 to 0.4 mm
• C. 3 to 5 mm
• D. 40 to 60 mm

Explanation: Metallic shielding is normally made from a very thin metal tape or layer, commonly about 0.04 mm thick.

• A. presence of moisture
• B. working temperature
• C. time of application of the voltage
• D. all of the above

Explanation: Cable breakdown is affected by moisture, temperature and the duration of voltage application because these change insulation strength and…

• A. more perfect impregnation
• B. smaller overall size
• C. no ionisation, oxidation and formation of voids
• D. all of the above

Explanation: Oil fills voids in the insulation, improves impregnation and suppresses ionisation and oxidation, allowing a more compact cable design.

• A. annealed
• B. hardened and tempered
• C. hard drawn
• D. alloy with chromium

Explanation: Cable conductors are generally made from annealed copper because heat treatment makes copper soft, flexible and easy to draw into strands.

• A. mica insulated
• B. paper insulated
• C. compressed oil or compressed gas insulated
• D. rubber insulated
• E. none of the above

Explanation: At 220 kV, conventional solid insulation becomes difficult to use economically because of high electric stress and capacitance.

• A. 2 cm
• B. 10 cm
• C. 50 cm
• D. 400 cm

Explanation: Keeping parallel power and communication cables about 50 cm apart reduces inductive and electromagnetic interference from the power cable.

• A. low permittivity
• B. high resistivity
• C. high dielectric strength
• D. all of the above

Explanation: A good insulator has high resistivity to limit leakage, high dielectric strength to withstand voltage, and low permittivity to reduce…

• A. it is hygroscopic
• B. it has high capacitance
• C. it is an organic material
• D. none of the above

Explanation: Paper readily absorbs moisture because it is hygroscopic, and absorbed moisture sharply reduces its insulation resistance and dielectric…