Free Power Systems MCQs with Answers
334 Power Systems MCQs from Electrical Engineering, each with the correct answer and a written explanation of why it is correct. Free and unlimited, with no account needed.
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334 questions · page 12 of 17
- A. higher
- B. lower
- C. same as long as initial pressure and temperature is unchanged
- D. none of the above
Explanation: A condenser reduces the exhaust pressure and permits greater expansion of the steam, increasing the turbine work and thermal efficiency.
Correct answer: higher- A. increases with the increase in number of stages
- B. decreases with the increase in number of stages
- C. remains same irrespective of number of stages
- D. none of the above
Explanation: The reheat factor is the ratio of the sum of stagewise actual enthalpy drops to the overall isentropic enthalpy drop.
Correct answer: increases with the increase in number of stages- A. Throttle governing
- B. Nozzle control governing
- C. By-pass governing
- D. all of the above
Explanation: Steam turbines may be controlled by throttling the inlet steam, regulating flow through selected nozzles, or admitting steam through a…
Correct answer: all of the above- A. 0.5 to 0.6
- B. 0.9 to 0.95
- C. 1.02 to 1.06
- D. 1.2 to 1.6
Explanation: Because stagewise expansion losses accumulate, the reheat factor is slightly greater than unity, normally about 1.02 to 1.06.
Correct answer: 1.02 to 1.06- A. 75%
- B. 100%
- C. 50%
- D. 60%
Explanation: In a Parsons turbine, the enthalpy drop is divided equally between the fixed and moving blades.
Correct answer: 50%- A. pressure compounded steam turbine
- B. simple single wheel, impulse steam turbine
- C. simple single wheel reaction steam turbine
- D. multi wheel reaction steam turbine
Explanation: A Parsons turbine is a multistage reaction turbine, commonly described as a multi-wheel reaction turbine.
Correct answer: multi wheel reaction steam turbine- A. reaction steam turbine
- B. velocity compounded impulse steam turbine
- C. pressure compounded impulse steam turbine
- D. pressure velocity compounded steam turbine
Explanation: The Rateau arrangement divides the total pressure drop among several stages, with each stage operating on the impulse principle.
Correct answer: pressure compounded impulse steam turbine- A. there is enthalpy drop both in fixed and moving blades
- B. there is enthalpy drop only in fixed blades
- C. there is enthalpy drop only in moving blades
- D. none of the above
Explanation: A reaction turbine has pressure and enthalpy drops in both the stationary and moving blade passages.
Correct answer: there is enthalpy drop both in fixed and moving blades- A. near bottom of chimney
- B. near bottom of furnace
- C. at the top of the chimney
- D. anywhere permissible
Explanation: In an induced-draught system, the fan is placed in the hot-gas path between the boiler and chimney, commonly near the bottom of the…
Correct answer: near bottom of chimney- A. less smoke
- B. more draught
- C. less chimney gas temperature
- D. all of the above
Explanation: Artificial draught improves combustion, reduces smoke, and allows the gases to leave with a lower temperature than in poorly controlled…
Correct answer: all of the above- A. air fans
- B. steam jet
- C. fan or steam jet
- D. all of the above
Explanation: Artificial draught is created mechanically by fans or pneumatically by steam jets. Therefore, both a fan and a steam jet can produce it.
Correct answer: all of the above- A. less
- B. more
- C. same
- D. not predictable
Explanation: An induced-draught fan handles hot flue gases, whose volume is larger than that of the relatively cool air handled by a forced-draught fan…
Correct answer: more- A. forced fan
- B. chimney
- C. steam jet
- D. only motion of locomotive
Explanation: Locomotive boilers commonly use the exhaust steam jet in the smokebox to draw flue gases through the firebox and boiler tubes.
Correct answer: steam jet- A. to produce draught to accelerate the combustion of fuel
- B. to discharge gases high up in the atmosphere to avoid hazard
- C. to reduce the temperature of the hot gases discharged
- D. none of the above
Explanation: With forced draught, the fan supplies the combustion air, so the chimney is not primarily needed to create draught.
Correct answer: to discharge gases high up in the atmosphere to avoid hazard- A. less
- B. more
- C. same
- D. may be more or less
Explanation: For equal height, a steel chimney generally produces more draught because it heats up quickly and maintains hotter gases, while its smooth…
Correct answer: more- A. decreases if the chimney gas temperature increases
- B. increases if the chimney gas temperature increases
- C. remains same irrespective of chimney gas temperature
- D. may increase or decrease
Explanation: Chimney draught increases when the chimney gases become hotter because their density falls, increasing the pressure difference between the…
Correct answer: increases if the chimney gas temperature increases- A. decreases with increase in outside air temperature
- B. increases with increase in outside air temperature
- C. remains the same irrespective of outside air temperature
- D. may increase or decrease with increase in outside air temperature
Explanation: Draught depends on the density difference between outside air and chimney gases.
Correct answer: decreases with increase in outside air temperature- A. induced draught
- B. natural draught
- C. forced draught
- D. balanced draught
Explanation: A chimney creates draught naturally through the density difference between hot flue gases and cooler outside air, without a fan.
Correct answer: natural draught- A. impulse turbines
- B. reaction turbines
- C. impulse-reaction turbines
- D. none of the above
Explanation: Most modern steam turbines use impulse-reaction stages, combining pressure drop in fixed and moving blades.
Correct answer: impulse-reaction turbines- A. air
- B. feed water
- C. flue gases
- D. all above
Explanation: An economiser recovers heat from flue gases to preheat the boiler feed water before it enters the boiler.
Correct answer: feed water