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 151 of 158
- A. chain grate
- B. spreader
- C. travelling grate
- D. all of the above
Explanation: Chain-grate, spreader, and travelling-grate stokers all feed coal onto the upper surface of the burning fuel bed, so each is an overfeed…
Correct answer: all of the above3002. Under-feed stokers work best for _________ coals high in volatile matter and with caking tendency?
- A. anthracite
- B. lignite
- C. semibituminous and bituminous
Explanation: Underfeed stokers are suitable for semibituminous and bituminous coals because these coals contain relatively high volatile matter and can…
Correct answer: semibituminous and bituminous- A. unit
- B. central
- C. none of the above
Explanation: In a central system, one central pulverizer prepares the fuel and sends it to a bunker before distribution to individual burners.
Correct answer: central- A. primary air
- B. secondary air
- C. tertiary air
Explanation: Secondary air is introduced around or above the fuel stream to supply the oxygen needed to complete combustion.
Correct answer: secondary air- A. carrying coal in horizontal direction
- B. carrying coal in vertical direction
- C. carrying coal in any direction
Explanation: A bucket elevator carries bulk material in buckets along a vertical path, lifting coal from a lower level to a higher one.
Correct answer: carrying coal in vertical direction- A. lift trucks
- B. coal accelerators
- C. tower cranes
- D. belt conveyor
Explanation: Coal accelerators are used to unload coal in small power plants by rapidly discharging it from transport vehicles or containers.
Correct answer: coal accelerators- A. 20 to 40 tonnes/hr
- B. 50 to 100 tonnes/hr
- C. 100 to 150 tonnes/hr
- D. 150 to 200 tonnes/hr
Explanation: A typical belt conveyor used in coal handling has a capacity of roughly 50 to 100 tonnes per hour, although the actual value depends on…
Correct answer: 50 to 100 tonnes/hr- A. dust
- B. clinkers
- C. iron particles
- D. sand
Explanation: Magnetic separators attract ferrous contaminants, particularly iron particles, from coal before it reaches crushers and other equipment.
Correct answer: iron particles- A. reduce the flame length
- B. increase the flame length
- C. transport and dry the coal
- D. provide air round the burners for getting optimum combustion
Explanation: Secondary air is admitted around the burner to provide sufficient oxygen and mixing for complete, well-controlled combustion.
Correct answer: provide air round the burners for getting optimum combustion- A. reduce the flame length
- B. increase the flame length
- C. transport and dry the coal
- D. provide air around burners for get¬ting optimum combustion
Explanation: Primary air carries pulverised coal from the mill to the burners and also dries it during transport.
Correct answer: transport and dry the coal- A. burn completely
- B. burn freely
- C. do not form ash
- D. form lumps or masses of coke
Explanation: Caking coal softens and fuses when heated, producing coherent lumps or masses of coke.
Correct answer: form lumps or masses of coke- A. 20 to 100 MW
- B. 50 to 300 MW
- C. 70 to 400 MW
- D. 100 to 650 MW
Explanation: In the conventional classification used for power-station equipment, large turbo-generators generally have ratings from about 50 to 300…
Correct answer: 50 to 300 MW- A. 1 to 5%
- B. 4 to 10%
- C. 10 to 12%
Explanation: An economiser transfers heat from boiler flue gases to the feedwater, reducing the fuel required to produce steam.
Correct answer: 4 to 10%- A. 20 kgf/cm2
- B. 50 kgf/cm2
- C. 100 kgf/cm2
- D. 150 kgf/cm2
Explanation: Modern steam-station boilers operate at high pressures, commonly of the order of 150 kgf/cm² in the textbook context of this question.
Correct answer: 150 kgf/cm2- A. center of coal fields
- B. center of maximum load of equipments
- C. center of gravity of electrical system
Explanation: The load centre is the electrical equivalent of the centre of gravity of the system, determined from the distribution of loads.
Correct answer: center of gravity of electrical system3016. The efficiency of a modern boiler using coal and heat recovery equipment is about_____________?
- A. 25 to 30%
- B. 40 to 50%
- C. 65 to 70%
- D. 85 to 90%
Explanation: With coal combustion plus heat-recovery equipment such as economisers, air preheaters and superheaters, modern boiler efficiency is…
Correct answer: 85 to 90%- A. 30 metres
- B. 40 metres
- C. 60 metres
- D. 100 metres
Explanation: A screw conveyor is suitable for relatively short coal-handling runs because friction, power demand and alignment problems increase with…
Correct answer: 30 metres- A. 30°
- B. 60°
- C. 80°
- D. 90°
Explanation: A conventional belt conveyor can transport coal on inclines up to approximately 30 degrees, although the practical angle depends on belt…
Correct answer: 30°- A. condensing type
- B. non-condensing type
- C. none of the above
Explanation: Steam power stations commonly use condensing turbines because exhaust steam is condensed and returned as feedwater, while the vacuum at…
Correct answer: condensing type- A. four
- B. three
- C. two
- D. one
Explanation: Two safety valves provide protection against excessive boiler pressure, while allowing one valve to remain effective if the other requires…
Correct answer: two