Free Wiring, Installation and Safety MCQs with Answers

• A. inadequate motor wiring
• B. poorely regulated power supply
• C. any one of the above
• D. none of the above

Explanation: Voltage drop at motor terminals can result from undersized or inadequate wiring, or from a poorly regulated supply.

• A. lead
• B. paper
• C. rubber
• D. none of the above

Explanation: Impregnated paper has high dielectric strength and was the traditional insulation for high-voltage cables.

• A. square conductors
• B. circular conductors
• C. rectangular conductors
• D. sector-shaped conductors
• E. none of the above

Explanation: Sector-shaped conductors fit together with less empty space than circular conductors, giving a smaller overall multicore cable.

• A. 110 V
• B. 210 V
• C. 230 V
• D. 400 V

Explanation: The nominal single-phase supply to residential consumers in Pakistan is 230 V.

• A. The oil may loose its viscosity and it may start drawing off from higher levels
• B. Expansion of the oil may cause the sheath to burst
• C. Unequal expansion may create voids in the insulation which will lead to ionization
• D. The thermal instability may rise due to the rapid increase of dielectric losses with temperature
• E. All of the above

Explanation: Excessive cable temperature can reduce oil viscosity, expand the oil, create insulation voids through unequal expansion, and increase…

• A. Direct laying
• B. Draw-in-system
• C. Solid system
• D. All of the above

Explanation: Underground cables may be installed by direct laying in trenches, by pulling them through ducts in a draw-in system, or by embedding them…

• A. arcs across separating contacts
• B. mechanical noise of high intensity
• C. both mechanical noise and arc between contacts
• D. none of the above

Explanation: Opening the switch can produce an arc across the separating contacts, and the rapidly changing current generates radio-frequency…

• A. very low
• B. low
• C. high
• D. any value

Explanation: A high-wattage test lamp has lower resistance and allows substantial current to pass when connected in series with an appliance…

• A. parallel
• B. series
• C. series-parallel
• D. end-to-end

Explanation: Street-lighting lamps are connected in parallel so each receives the full supply voltage and operates independently.

• A. the magnitude of voltage on the conductor
• B. the magnitude of current flowing through it
• C. both A. and (b)
• D. none of the above

Explanation: Insulation thickness is mainly selected to withstand the conductor's voltage and prevent dielectric breakdown.

• A. to prevent leakage of current
• B. to prevent shock
• C. both of above factors
• D. none of above factors

Explanation: Insulation keeps current from escaping to surrounding materials and also prevents a person from touching a live conductor.

• A. ampere-hours
• B. ampere-volts
• C. kWh
• D. amperes

Explanation: A fuse is selected according to the maximum current it can carry safely before melting, so its rating is given in amperes.

• A. Copper
• B. Gold
• C. Silver
• D. Paper

Explanation: Paper is an insulating material because it has very high electrical resistance and does not allow free movement of charge.

• A. Cast iron
• B. Copper
• C. Carbon
• D. Tungsten

Explanation: Copper is an excellent conductor, so it is not a poor conductor. Cast iron, carbon, and tungsten have considerably higher resistivity than…

• A. High speed operation
• B. High rupturing capacity
• C. No ageing effect
• D. All of the above

Explanation: HRC fuses interrupt large fault currents safely, operate quickly, and are less affected by ageing than rewirable fuses.