Free Power Systems MCQs with Answers

• A. 62 x 10^5 V/m
• B. 72 x 10^5 V/m
• C. 82 x 10^5 V/m
• D. 92 x 10^5 V/m

Explanation: For a single-core cable, maximum stress occurs at the conductor surface: g_max = V/[r ln(R/r)].

• A. kW
• B. kVA
• C. kVAR
• D. volts

Explanation: A capacitor supplies reactive power, so a power-factor-correction bank is rated in kVAR rather than real power in kW or apparent power in…

• A. solar cells
• B. dry cells
• C. nickel-cadmium cells
• D. lead-acid batteries

Explanation: Solar cells convert sunlight directly into electrical energy, making them the standard continuous power source for satellites.

• A. very low
• B. low
• C. medium
• D. high

Explanation: Skin effect is caused by electromagnetic induction within a conductor and becomes significant at high frequency, forcing more current…

• A. 200 Hz
• B. 100 Hz
• C. 60 Hz
• D. 50 Hz

Explanation: Pakistan uses a 50 Hz, 230/400 V power system, matching the standard frequency used across much of Asia and Europe.

• A. to reduce line losses
• B. to maximise the utilization of the capacities of generators, lines and transformers
• C. to reduce voltage regulation of the line
• D. due to all above reasons

Explanation: A high power factor reduces current for a given real power, lowering line losses and voltage drop.

• A. reduces load handling capability of electrical system
• B. results in more power losses in the electrical system
• C. overloads alternators, transformers and distribution lines
• D. results in more voltage drop in the line
• E. results in all above

Explanation: A poor power factor requires higher current for the same useful power, causing greater losses, voltage drop, and loading of alternators…

• A. kW
• B. kVA
• C. kV
• D. kVAR

Explanation: Power-factor-correction capacitors supply leading reactive power, so their rating is expressed in volt-amperes reactive, or kVAR.

• A. very near to inductive load
• B. across the terminals of the inductive load
• C. far away from the inductive load
• D. any where

Explanation: A capacitor should be connected across the inductive load so it supplies the required leading reactive current locally and reduces the…

• A. plant capacity
• B. average load
• C. peak load
• D. kWh generated

Explanation: Diversity factor compares the sum of individual maximum demands with the simultaneous maximum demand of the system.

• A. Switching of the loads
• B. Frequency reduction
• C. Voltage reduction
• D. Any of the above

Explanation: Load shedding can be achieved by disconnecting selected loads, reducing frequency, or reducing voltage to lower demand.

• A. Horn gaps
• B. Rod gaps
• C. Surge absorbers
• D. All of the above

Explanation: Horn gaps, rod gaps and surge absorbers all provide paths or attenuation for lightning surges, protecting insulation and equipment from…

• A. Steam turbine
• B. Condenser
• C. Water treatment plant
• D. Boiler

Explanation: The boiler operates under high temperature and pressure and contains many tubes, valves and auxiliary systems, making inspection, cleaning…

• A. Diesel engine plant
• B. Gas turbine plant
• C. Nuclear power plant
• D. Pumped storage plant

Explanation: Nuclear plants have high capital cost, low operating cost and limited load-following ability, so they are most economical when run…

• A. Solar energy
• B. Geothermal power
• C. Wind power
• D. iMHD

Explanation: MHD power generation was largely experimental and lacked the established reliability of conventional sources, making it the least reliable…

• A. Sinking fund method
• B. Straight line method
• C. Diminishing value method
• D. Halsey's 50-50 formula

Explanation: Sinking-fund, straight-line and diminishing-value methods are recognized depreciation methods.

• A. 15 to 20 years
• B. 20 to 50 years
• C. 50 to 75 years
• D. 75 to 100 years

Explanation: Diesel generating sets experience substantial mechanical wear and generally have a shorter service life than steam or hydroelectric…

• A. Improved frequency of power supplied
• B. Reduction in total installed capacity
• C. Increased reliability
• D. Economy in operation of plants

Explanation: Interconnection commonly improves reliability, permits economy of operation and reduces the required total installed or reserve capacity.

• A. Electric clock
• B. Mixer grinder
• C. Ceiling fan
• D. Room heater

Explanation: A room heater is essentially a resistive load, so its operation is practically independent of supply frequency, unlike clocks, fans and…

• A. remains unchanged
• B. decreases
• C. increases
• D. none of the above

Explanation: Interconnecting systems allows their individual maximum demands to occur at different times, so the combined maximum demand is relatively…