Free Wiring, Installation and Safety MCQs with Answers

• A. Cost
• B. Durability
• C. Compliance with performance criteria as laid down in specifications
• D. All of the above

Explanation: A sound design must satisfy the specified performance requirements while also being economical and sufficiently durable.

• A. paper mills
• B. steel mills
• C. moist atmospheres
• D. explosive atmospheres

Explanation: Flame-proof motors are enclosed so that any internal spark or flame does not ignite the surrounding atmosphere.

• A. A mechanical
• B. An electronic
• C. An electromechanical
• D. None of the above

Explanation: A relay combines an electrical coil with mechanically moving contacts, so it is classified as an electromechanical switch.

• A. smoky and dirty atmosphere
• B. humidity in the atmosphere
• C. both (A) and (b)
• D. neither (A) nor (b)

Explanation: Moisture forms a partially conducting film on an insulator, while smoke and dirt provide or retain contaminating conductive paths.

• A. Aluminium is more ductile and malleable than copper
• B. Aluminium is available in plenty, cheaper and lighter than copper
• C. Aluminium has lower resistivity than that of copper
• D. Aluminium has less temperature co-efficient than copper

Explanation: Aluminium is widely used instead of copper because it is more abundant, cheaper, and much lighter, although its resistivity is higher.

• A. Porcelain
• B. Slate
• C. Asbestos
• D. Glass

Explanation: Spark plugs use porcelain as the insulator because it withstands high temperature, high voltage, and chemical attack inside an engine.

• A. Both have great tendency for oxidation
• B. Both have low melting point
• C. Very large length of wires will be required
• D. All of the above

Explanation: Copper and aluminium have low resistivity, so impractically long wires would be needed to obtain the resistance required for heating; they…

• A. Tungsten
• B. Aluminium
• C. Copper
• D. Carbon

Explanation: Among the listed materials, copper has the lowest resistivity and therefore the highest electrical conductivity.

• A. Less liability to kink
• B. Greater flexibility
• C. Less liability to break
• D. All of the above

Explanation: Stranding makes a conductor more flexible, reduces its tendency to kink, and allows it to withstand repeated bending without breaking as…

• A. transformer, motor and generator windings
• B. transmission and distribution lines
• C. house wiring
• D. all above applications

Explanation: Low-resistivity conductors reduce I²R losses and voltage drop, so they are used in machine windings, transmission and distribution lines…

• A. Kanthal
• B. Manganin
• C. Nichrome
• D. Eureka

Explanation: Kanthal is an iron-chromium-aluminium resistance alloy capable of operating at very high temperatures, generally higher than Nichrome…

• A. a ceramic body having metal and caps
• B. a wire of platinum
• C. a heavy cross-section of copper or aluminium
• D. a ceramic tube having carbon rod inside it

Explanation: An H.R.C. fuse has a heat-resistant ceramic body with metal end caps and a calibrated fuse element inside.

• A. maximum fault current carrying through the ground wire
• B. rated current carrying capacity of the service line
• C. depends on the soil resistance
• D. both (A) and (C)

Explanation: Grounding design must provide a safe path for the prospective fault current, while soil resistance affects how effectively the grounding…

• A. only for the safety of the equipment
• B. only for the safety of the operating personnel
• C. both (A) and (B)
• D. none of the above

Explanation: Grounding protects equipment by limiting dangerous voltages and enables protective devices to clear faults, while also reducing shock risk…

• A. depth of the electrode
• B. moisture
• C. Nacl
• D. all the above

Explanation: Soil resistance varies with electrode depth, moisture content, and dissolved salts such as sodium chloride.

• A. to provide as low resistance possible to the ground
• B. to provide as high resistance possible to the ground
• C. to provide flow of positive, negative and zero sequence currents
• D. none of the above

Explanation: Earthing provides a low-resistance path for fault current to flow safely into the ground, allowing protective devices to operate quickly.

• A. to provide low impedance
• B. to discharge the charging capacitance to ground
• C. protection for operating personnel
• D. both (B) and (C)

Explanation: An isolated EHV apparatus may retain charge on its capacitance even after disconnection.

• A. increase
• B. decrease
• C. does not affect
• D. none of the above

Explanation: Moisture increases the soil's conductivity by providing ions for current flow, so the earth resistance decreases.

• A. voltage potential at the earth mat increases due to grounding
• B. voltage potential at the earth mat decreases due to grounding
• C. voltage potential at the earth mat remains zero irrespective of fault
• D. none of the above

Explanation: During an earth fault, fault current flows through the grounding conductor and earth mat, producing a voltage rise relative to remote…

• A. grounding resistance should be as low as possible
• B. grounding resistance should be as high as possible
• C. grounding resistance should be always zero
• D. none of the above

Explanation: Low grounding resistance keeps fault current high enough to operate protective devices and limits the voltage rise of exposed metalwork.