All Free Electrical Engineering MCQs with Answers
Every Electrical Engineering question in the bank, across all chapters, each with the correct answer and a written explanation. Free and unlimited, with no account needed.
3,143 questions · page 145 of 158
- A. Oil circuit breakers
- B. Air blast circuit breakers
- C. Minimum oil circuit breakers
- D. All of the above
Explanation: Routine tests such as insulation, mechanical operation and timing checks are performed on oil, air-blast and minimum-oil circuit breakers.
Correct answer: All of the above- A. copper tungsten alloy
- B. porcelain
- C. electrolytic copper
- D. aluminium alloy
Explanation: Arcing contacts must withstand high temperature, erosion and repeated arcing, so copper-tungsten alloys are commonly used.
Correct answer: copper tungsten alloy- A. a capackive reactance
- B. an inductive reactance
- C. a resistance increasing with voltage rise across the arc
- D. a resistance decreasing with voltage rise across the arc
Explanation: An arc has a negative resistance characteristic: as the voltage across the arc rises, its effective resistance generally falls because…
Correct answer: a resistance decreasing with voltage rise across the arc- A. fuses
- B. relays
- C. fast switches
- D. circuit breakers
Explanation: Fault diverters are high-speed switches that divert or interrupt fault current before serious equipment damage occurs.
Correct answer: fast switches- A. delayed
- B. instantaneous
- C. both of the above
- D. none of the above
Explanation: A magnetic circuit breaker uses the strong magnetic field produced by a fault current to trip immediately.
Correct answer: instantaneous- A. delayed trip action
- B. instantaneous trip action
- C. both of the above
- D. none of the above
Explanation: A thermal circuit breaker uses a bimetallic strip that heats and bends under sustained excess current, producing a time delay before…
Correct answer: delayed trip action- A. Battery charging work
- B. Arc welding
- C. Electrolytic and electro-chemical processes
- D. Arc lamps for search lights
- E. All of the aboveCompare Local Schools
Explanation: DC supplies are used for battery charging, arc welding, electrochemical processes, and certain arc-lamp applications such as searchlights.
Correct answer: All of the aboveCompare Local Schools- A. earth
- B. conduction
- C. sheath
- D. insulator
Explanation: In a cable capacitor, the electric field varies inversely with radius, so it is greatest at the surface of the inner conductor.
Correct answer: conduction- A. insulation
- B. conductor
- C. outer sheath
- D. uniformly all over
Explanation: In a cable, the electric stress is greatest at the conductor surface and decreases outward, reaching its minimum at the inner surface of…
Correct answer: insulation- 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)].
Correct answer: 72 x 10^5 V/m2891. The capacity of capacitor bank used in power factor correction is expressed in terms of____________?
- 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…
Correct answer: kVAR- 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.
Correct answer: solar cells- 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…
Correct answer: high- 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.
Correct answer: 50 Hz- 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.
Correct answer: due to all above reasons- 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…
Correct answer: results in all above- 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.
Correct answer: 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…
Correct answer: across the terminals of the inductive load- 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.
Correct answer: plant capacity- 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.
Correct answer: Any of the above