All Free Electrical Engineering MCQs with Answers

• A. aluminium
• B. steel
• C. brass
• D. copper

Explanation: Steel is generally used for cable armour because its high mechanical strength protects the cable against impact, crushing and tension.

• A. copper
• B. wood
• C. R.C.C.
• D. steel

Explanation: Transmission-line cross-arms are generally made of steel because it provides the required mechanical strength and durability for…

• A. copper conductors
• B. all aluminium conductors
• C. A.C.S.R. conductors
• D. none of these

Explanation: ACSR combines aluminium strands, which give low weight and good conductivity, with a steel core that provides mechanical strength.

• A. unity
• B. lagging
• C. leading
• D. zero

Explanation: Industrial loads contain many induction motors and transformers, both of which draw magnetising current and therefore operate at a lagging…

• A. balanced
• B. unbalanced
• C. either of the above
• D. none of the above

Explanation: Distributor loads are usually spread unevenly among single-phase and three-phase consumers, so their phase currents are generally…

• A. suspension insulators
• B. pin insulators
• C. both A. and B.
• D. none of the above

Explanation: Suspension insulators are used on high-voltage transmission lines because strings of units can support greater voltage and mechanical…

• A. single phase
• B. three-phase three wire
• C. three-phase four wire
• D. none of the above

Explanation: Residential distributors generally use a three-phase, four-wire system, with the neutral providing single-phase supply to homes and…

• A. underground
• B. overhead
• C. either of the above
• D. none of the above

Explanation: Most high-voltage transmission lines in Pakistan are overhead because overhead construction is much cheaper and easier to inspect and…

• A. Radial system
• B. Ring system
• C. Inter-connected system
• D. None of the above

Explanation: A radial distribution system has a single path from the source to each load, making its layout simple and its initial cost lowest.

• A. 6.6 kV
• B. 11 kV
• C. 33 kV
• D. 66 kV
• E. 132 kV

Explanation: In the usual cable-voltage classification, extra-high-tension cables operate up to 66 kV.

• A. 3.3 kV
• B. 6.6 kV
• C. 11 kV
• D. 33 kV

Explanation: Supertension cables are commonly classified for voltages up to 33 kV. The 11 kV value belongs to the usual high-tension cable range, not…

• A. l.lkV
• B. 3.3kV
• C. 6.6kV
• D. llkV

Explanation: The conventional classification places high-voltage cables up to 11 kV.

• A. Increase of short-circuit current of the system
• B. Availability of steady voltage at all loads at the line terminals
• C. Possibility of better protection for the line due to possible use of higher terminal reactants
• D. Improvement of power factor at times of moderate and heavy loads
• E. Possibility of carrying increased power for a given conductor size in case of long-distance heavy power transmission

Explanation: A constant-voltage transmission system requires low line impedance, which causes a larger short-circuit current when a fault occurs.

• A. surge impedance of the line
• B. conductance of the line
• C. regulation of the line
• D. none of the above

Explanation: The quantity √(Z/Y), where Z is series impedance and Y is shunt admittance per unit length, is the surge or characteristic impedance of a…

• A. Seeback effect
• B. Ferranti effect
• C. Raman effect
• D. none of the above

Explanation: The Ferranti effect is the rise of receiving-end voltage above sending-end voltage when a long line is open-circuited or lightly loaded.

• A. a long line
• B. a medium line
• C. a short line
• D. any of the above

Explanation: Transmission lines longer than roughly 250 km are treated as long lines because distributed capacitance and inductance must be considered.

• A. Resistance
• B. Inductance
• C. Capacitance
• D. All of the above

Explanation: Resistance, inductance, capacitance, and conductance are the distributed constants of a transmission line.

• A. Size of the conductor
• B. Shape of the conductor
• C. Surface condition of the conductor
• D. All of the above

Explanation: Corona depends on conductor size, conductor shape, and surface condition because these factors affect the electric-field intensity at the…

• A. 40-50 meters
• B. 60-100 meters
• C. 80-100 meters
• D. 300-500 meters

Explanation: R.C.C. poles are stronger and can support longer spans than ordinary wooden poles.

• A. stay wire
• B. earth wire
• C. structural components
• D. all of the above

Explanation: Galvanised steel resists atmospheric corrosion while providing good mechanical strength, so it is used for stay wires, earth wires and…