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MCQOPTIONS
This section includes 59 Mcqs, each offering curated multiple-choice questions to sharpen your Power Engineering knowledge and support exam preparation. Choose a topic below to get started.
| 1. |
Air enters the compressor of a gas turbine plant operating on Brayton cycle at 1 bar and 27°C. The pressure ratio in the cycle is 6. If the relation between the turbine work WT and compressor work WC is WT = 3WC and γ = 1.4, the cycle efficiency will be nearly |
| A. | 40% |
| B. | 50% |
| C. | 60% |
| D. | 70% |
| Answer» B. 50% | |
| 2. |
In a two-stage air compressor, an intercooler is placed |
| A. | before L.P. cylinder |
| B. | after H.P. cylinder |
| C. | in between L.P. and H.P. cylinder |
| D. | none of the above |
| Answer» D. none of the above | |
| 3. |
Consider a simple gas turbine (Brayton cycle) and a gas turbine with perfect regeneration. In both cycles, the pressure ratio is 8 and the ratio of specific heats of the working medium is 1.5. The ratio of minimum to maximum temperature is 0.2 (with temperature in K) in the regenerative cycle. The ratio of the thermal efficiency of the simple cycle to that of the regenerative cycle is |
| A. | 0.63 |
| B. | 0.73 |
| C. | 0.83 |
| D. | 0.93 |
| Answer» D. 0.93 | |
| 4. |
For the same compression ratio, the Brayton cycle efficiency is |
| A. | Same as the Diesel cycle efficiency |
| B. | Equal to the Otto cycle efficiency |
| C. | More than the Diesel cycle efficiency |
| D. | Less than the Otto cycle efficiency |
| Answer» C. More than the Diesel cycle efficiency | |
| 5. |
Group I shows different heat addition processes in power cycles. Likewise, Group II shows different heat removal processes. Group III lists power cycles. Match items from Groups I, II and III.Group IGroup IIGroup IIIP. Pressure constantS. Pressure constant1. Rankine cycleQ. Volume constantT. Volume constant2. Otto cycleR. Temperature constantU. Temperature constant3. Carnot cycle 4. Diesel cycle 5. Brayton cycle |
| A. | P – S – 5, R – U – 3, P – S – 1, Q – T - 2 |
| B. | P – S – 1, R – U – 3, P – S – 4, P – T - 2 |
| C. | R – T – 3, P – S – 1, P – T – 4, Q – S - 5 |
| D. | P – T – 4, R – S – 3, P – S – 1, P – S - 5 |
| Answer» B. P – S – 1, R – U – 3, P – S – 4, P – T - 2 | |
| 6. |
If power developed by a turbine in a certain steam power plant is 1200kW. Heat supplied to boiler is 3360 kJ/kg. The heat rejected by the system to cooling water is 2520 kJ/kg, and feed pump work required to condensate back into boiler is 6kW, then the mass rate of flow through the cycle will be |
| A. | 1.421 kg/s |
| B. | 14.21 kg/s |
| C. | 0.1421 kg/s |
| D. | 0.01421 kg/s |
| Answer» B. 14.21 kg/s | |
| 7. |
A steam thermal power plant work on |
| A. | Bryton cycle |
| B. | Rankine cycle |
| C. | Carnot cycle |
| D. | Otto cycle |
| Answer» C. Carnot cycle | |
| 8. |
Boilers in the Rankine cycle are used: |
| A. | to allow expansion of steam |
| B. | to store working fluid |
| C. | for steam generation |
| D. | to maintain heat in the process |
| Answer» D. to maintain heat in the process | |
| 9. |
In a two stage gas turbine plant, with intercooling and reheating |
| A. | Both work ratio and thermal efficiency increase |
| B. | Work ratio increases but thermal efficiency decreases |
| C. | Thermal efficiency increase but work ratio decreases |
| D. | Both work ratio and thermal efficiency decrease |
| Answer» C. Thermal efficiency increase but work ratio decreases | |
| 10. |
In a good steam power plant, the Rankine cycle efficiency is in the range of: |
| A. | 75 – 85% |
| B. | 15 – 25% |
| C. | 65 – 75% |
| D. | 35 – 45% |
| Answer» E. | |
| 11. |
Above critical pressure ratio, addition of regenerator in Brayton cycle causes one of the following: |
| A. | no effect in cycle efficiency |
| B. | lower compressor discharge temperature than turbine exhaust gas temperature |
| C. | gain in cycle efficiency |
| D. | loss in cycle efficiency |
| Answer» E. | |
| 12. |
An ideal Brayton cycle, operating between the pressure limits of 1 bar and 6 bar, has minimum and maximum temperatures of 300 K and 1500 K. The ratio of specific heats of the working fluid is 1.4. The approximate final temperatures (in K) at the end of the compression and expansion processes are respectively |
| A. | 500 and 900 |
| B. | 900 and 500 |
| C. | 500 and 500 |
| D. | 900 and 900 |
| Answer» B. 900 and 500 | |
| 13. |
Brayton cycle process is |
| A. | Two isentropic and two constant volumes |
| B. | Two isentropic and two constant pressures |
| C. | One constant pressure, one constant volume, two adiabatics |
| D. | Two isothermals and constant volume and constant pressure |
| Answer» C. One constant pressure, one constant volume, two adiabatics | |
| 14. |
In a steam power plant, the working fluid is: |
| A. | oil |
| B. | water |
| C. | diesel |
| D. | natural gas |
| Answer» C. diesel | |
| 15. |
In a gas turbine cycle, the turbine output is 600 kJ/kg, the compressor work is 400 kJ/kg, and the heat supplied is 1000 kJ/kg. the thermal efficiency of the cycle is: |
| A. | 20% |
| B. | 40% |
| C. | 30% |
| D. | 50% |
| Answer» B. 40% | |
| 16. |
For maximum discharge of hot gases through a chimney, the height of hot column producing draught is |
| A. | Twice the height of chimney |
| B. | Equal to the height of chimney |
| C. | Half the height of chimney |
| D. | None of the above |
| Answer» C. Half the height of chimney | |
| 17. |
A power plant usually works on |
| A. | Otto cycle |
| B. | Binary vapour cycle |
| C. | Brayton cycle |
| D. | Rankine cycle |
| Answer» E. | |
| 18. |
Efficiency of Brayton cycle is given by [where ‘r’ is the pressure ratio, γ = specific heat ratio] |
| A. | \(\eta = 1 - \frac{1}{{{r^{\gamma - 1}}}}\) |
| B. | \(\eta = 1 - \frac{1}{r}\) |
| C. | \(\eta = 1 - \frac{1}{{r^\gamma }}\) |
| D. | \(\eta = 1 - \frac{1}{{{r^{\left( {\gamma - 1} \right)/\gamma }}}}\) |
| Answer» E. | |
| 19. |
In a Ranking cycle, the work done by turbine during expansion of steam is 8 kJ while the work required for pump to feedback the water into the boiler is 6 kJ. Determine the work ratio. |
| A. | 0.9 |
| B. | 0.25 |
| C. | 0.34 |
| D. | 0.75 |
| Answer» C. 0.34 | |
| 20. |
High air-fuel ratio in a gas turbine |
| A. | Increases power output |
| B. | Improves thermal efficiency |
| C. | Reduces exhaust temperature |
| D. | Do not damage turbine blades |
| Answer» D. Do not damage turbine blades | |
| 21. |
Higher efficiency during the regeneration process in ‘Rankine cycle’ is because of: |
| A. | Heat is added before steam enters the low-pressure turbine |
| B. | The average temperature of heat addition in the boiler increases |
| C. | The total work delivered by the turbine increases |
| D. | The pressure inside the boiler increases |
| Answer» C. The total work delivered by the turbine increases | |
| 22. |
0.5 kg/s of steam of enthalpy 3140 kJ/kg enters a steam turbine. It leaves the turbine with an enthalpy of 2640 kJ/kg. The turbine’s power output is: |
| A. | 177 kW |
| B. | 500 kW |
| C. | 250 kW |
| D. | 102.5 kJ/s |
| Answer» D. 102.5 kJ/s | |
| 23. |
In jet engines, for efficient production of large power, fuel is burnt in an atmosphere of |
| A. | Vacuum |
| B. | Atmospheric air |
| C. | Compressed air |
| D. | Oxygen alone |
| Answer» D. Oxygen alone | |
| 24. |
In Rankine cycle, adiabatic enthalpy drop across the prime moves is 840 kJ/kg. the enthalpy of steam supplied is 294 kJ/kg. If the back pressure is 0.1 bar, then the specific steam consumption is (assume hf at 0.1 bar = 191.8 kJ/kg): |
| A. | 2.4 kg/kWh |
| B. | 4.2 kg/kWh |
| C. | 12.4 kg/kWh |
| D. | 3.4 kg/kWh |
| Answer» C. 12.4 kg/kWh | |
| 25. |
In a power plant, water (density = 1000 kg/m3) is pumped from 80 KPa to 3 MPa. The pump has an isentropic efficiency of 0.85. Assuming that the temperature of the water remains the same, the specific work (in kJ/kg) supplied to the pump is |
| A. | 0.34 |
| B. | 2.48 |
| C. | 2.92 |
| D. | 3.43 |
| Answer» E. | |
| 26. |
For the same maximum and minimum temperatures, the Rankine cycle has: |
| A. | more efficiency than that of the Carnot cycle |
| B. | equal efficiency to that of the Carnot cycle |
| C. | lower specific work output than that of the Carnot cycle |
| D. | higher specific work output than that of the Carnot cycle |
| Answer» E. | |
| 27. |
Air standard efficiency is also called: |
| A. | actual efficiency |
| B. | ideal efficiency |
| C. | overall efficiency |
| D. | effective efficiency |
| Answer» C. overall efficiency | |
| 28. |
If dry saturated steam is admitted to a steam turbine following an isentropic process, at the exit of the turbine, it will be a: |
| A. | Superheated steam |
| B. | Dry saturated steam |
| C. | Liquid condensate |
| D. | Wet steam |
| Answer» E. | |
| 29. |
A single stage impulse turbine is also known as |
| A. | Curtis stage turbine |
| B. | Reaction turbine |
| C. | De Laval turbine |
| D. | Rateau turbine |
| Answer» D. Rateau turbine | |
| 30. |
Consider the following statements:1) The thermal efficiency of the simple steam or Rankine cycle can be improved by increasing the maximum system pressure and temperature2) Increasing the superheat of the steam improves the specific work and decreases the moisture content of exhaust steam.3) Increasing maximum system pressure always increases the moisture content at the turbine exhaust4) Lowering the minimum system pressure increases the specific work of the cycleWhich of the above statements are correct |
| A. | 1, 2 and 3 |
| B. | 1, 2 and 4 |
| C. | 2, 3 and 4 |
| D. | 1, 3 and 4 |
| Answer» C. 2, 3 and 4 | |
| 31. |
In the Rankine cycle, the fluid which enters the boiler is: |
| A. | steam |
| B. | mercury |
| C. | water |
| D. | oxygen |
| Answer» D. oxygen | |
| 32. |
In a steam power plant the ratio of isentropic heat drop in the prime mover to the amount of heat supplied per unit mass of steam is known as |
| A. | Stage efficiency |
| B. | Degree reaction |
| C. | Rankine efficiency |
| D. | Relative efficiency |
| Answer» D. Relative efficiency | |
| 33. |
Identify the incorrect statement, from the following options related to the below statement:Superheated steam is used in a Rankine power cycle ______. |
| A. | Because steam at the exit of the turbine will be less wet, preventing erosion of turbine blades |
| B. | Because it increases work output of the cycle for the same pressure limit |
| C. | Because it increases cycle efficiency for the same pressure limit |
| D. | To reduce the work of pumping |
| Answer» E. | |
| 34. |
In Brayton cycle, the heat is rejected at ________. |
| A. | Constant temperature |
| B. | Constant pressure |
| C. | Constant volume |
| D. | Constant enthalpy |
| Answer» C. Constant volume | |
| 35. |
Gas turbine as compared to a steam turbine |
| A. | Requires less space for installation |
| B. | Has compressor and combustion chamber |
| C. | Has less efficiency |
| D. | All of these |
| Answer» E. | |
| 36. |
Binary vapour cycles are used to increase the |
| A. | Performance of the condenser |
| B. | Efficiency of the plant |
| C. | Output of the turbine |
| D. | Temperature of working fluid |
| Answer» C. Output of the turbine | |
| 37. |
Determine the correctness or otherwise of the following Assertion [a] and the Reason [r].Assertion [a]: Condenser is an essential equipment in a steam power plant.Reason [r]: For the same mass flow rate and the same pressure rise, a water pump requires substantially less power than a steam compressor. |
| A. | Both [a] and [r] are true and [r] is the correct reason for [a]. |
| B. | Both [a] and [r] are true but [r] is NOT the correct reason for [a]. |
| C. | [a] is true but [r] is false |
| D. | [a] is false and [r] is true. |
| Answer» C. [a] is true but [r] is false | |
| 38. |
A gas turbine works on |
| A. | Carnot cycle |
| B. | Brayton cycle |
| C. | Dual cycle |
| D. | Rankine cycle |
| Answer» C. Dual cycle | |
| 39. |
Air preheater is a part of |
| A. | Thermal power plant |
| B. | Wind power plant |
| C. | Nuclear power plant |
| D. | Hydel power plant |
| Answer» B. Wind power plant | |
| 40. |
Given below is an extract from steam tables.Temperature(°C) Psat(bar)Specific volume (m3 / kg)Enthalpy (kJ/Kg)Saturated liquidSaturatedvapourSaturatedliquidSaturatedvapour450.095930.00101015.26188.452394.8342.241500.0016580.0103371610.52610.5Specific enthalpy of water in kJ/kg at 150 bar and 45 °C is |
| A. | 203.6 |
| B. | 200.53 |
| C. | 196.38 |
| D. | 188.45 |
| Answer» E. | |
| 41. |
Consider the following statements in respect of gas turbines:A gas turbine plant with reheater leads to a1. Considerable improvement in the work output.2. Considerable improvement in the thermal efficiency.Which of the statements given above is/are correct? |
| A. | 1 only |
| B. | 2 only |
| C. | Both 1 and 2 |
| D. | Neither 1 nor 2 |
| Answer» B. 2 only | |
| 42. |
Identify the compressor for the PV diagram shown in figure. |
| A. | Single stage compressor |
| B. | Two stage compressor |
| C. | Two stage compressor with intercooling |
| D. | Two stage compressor with heat addition |
| Answer» D. Two stage compressor with heat addition | |
| 43. |
______ process is NOT involved in Rankine cycle. |
| A. | Isentropic compression |
| B. | Constant volume heat addition |
| C. | Constant pressure heat addition |
| D. | Isentropic expansion |
| Answer» C. Constant pressure heat addition | |
| 44. |
In Rankine cycle expansion of steam assumed to be |
| A. | Adiabatic |
| B. | Polytropic |
| C. | Isentropic |
| D. | Isothermal |
| Answer» D. Isothermal | |
| 45. |
In a simple single stage gas turbine plant, if T1 is the minimum temperature and T3 is the maximum temperature then what is the work ratio in terms of rP? |
| A. | \(1 - \frac {T_3}{T_1} (r_p)^\frac {\gamma - 1}{\gamma}\) |
| B. | \(1 - \frac {T_1}{T_3} (r_p)^\frac {\gamma - 1}{\gamma}\) |
| C. | \(1 - \frac {T_1}{T_3} (r_p)^\frac {\gamma}{\gamma - 1}\) |
| D. | \(1 - \frac {T_1}{T_3} (r_p)^\frac 1 {\gamma}\) |
| Answer» C. \(1 - \frac {T_1}{T_3} (r_p)^\frac {\gamma}{\gamma - 1}\) | |
| 46. |
Identify the incorrect statement, from the following options related to ‘Reheat in a Rankine cycle _____. |
| A. | Involves partial expansion of steam in successive turbine stages |
| B. | Produces higher Rankine cycle efficiency |
| C. | Result in lower average temperature of heat addition |
| D. | Addition of heat to steam in each reheat stage is done to raise its temperature |
| Answer» D. Addition of heat to steam in each reheat stage is done to raise its temperature | |
| 47. |
For a given set of operating pressure limits of a Rankine cycle the highest efficiency occurs for |
| A. | Saturated cycle |
| B. | Superheated cycle |
| C. | Reheat cycle |
| D. | Regenerative cycle |
| Answer» E. | |
| 48. |
In a Rankine cycle, the work output from a turbine is a change: |
| A. | in volume between the inlet and outlet |
| B. | in entropy between the inlet and outlet |
| C. | of enthalpy between the inlet and outlet |
| D. | in internal energy between the inlet and outlet |
| Answer» D. in internal energy between the inlet and outlet | |
| 49. |
A Rankine cycle consists of |
| A. | two isentropic processes and two constant volume processes |
| B. | two isothermal processes and two constant volume processes |
| C. | two isentropic processes and two constant pressure processes |
| D. | two isothermal processes and two constant pressure processes |
| Answer» D. two isothermal processes and two constant pressure processes | |
| 50. |
Gas turbine used in an aircraft is |
| A. | Close-cycle turbine |
| B. | Open-cycle turbine |
| C. | Constant-volume turbine |
| D. | None of the above |
| Answer» C. Constant-volume turbine | |