MCQOPTIONS
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MCQOPTIONS
This section includes 327 Mcqs, each offering curated multiple-choice questions to sharpen your GATE (Mechanical Engineering) knowledge and support exam preparation. Choose a topic below to get started.
| 1. |
A closed cycle gas turbine works on |
| A. | Carnot cycle |
| B. | Rankine cycle |
| C. | Ericsson cycle |
| D. | Joule cycle |
| Answer» E. | |
| 2. |
Gas turbine works on |
| A. | Brayton or Atkinson cycle |
| B. | Carnot cycle |
| C. | Rankine cycle |
| D. | Ericsson cycle |
| Answer» B. Carnot cycle | |
| 3. |
Gas turbine as compared to steam turbine |
| A. | Requires less space for installation |
| B. | Has compressor and combustion chamber |
| C. | Has less efficiency |
| D. | All of these |
| Answer» E. | |
| 4. |
Only rocket engines can be propelled to space because |
| A. | They can generate very high thrust |
| B. | They have high propulsion efficiency |
| C. | These engines can work on several fuels |
| D. | They are not air breathing engines |
| Answer» E. | |
| 5. |
A centrifugal compressor works on the principle of |
| A. | Conversion of pressure energy into kinetic energy |
| B. | Conversion of kinetic energy into pressure energy |
| C. | Centripetal action |
| D. | Generating pressure directly |
| Answer» C. Centripetal action | |
| 6. |
The volume of air sucked by the compressor during its suction stroke is called |
| A. | Free air delivery |
| B. | Compressor capacity |
| C. | Swept volume |
| D. | None of these |
| Answer» D. None of these | |
| 7. |
The weight per horse power ratio for gas in Turbine as compared to I.C. engine and steam turbine is |
| A. | Same |
| B. | Higher |
| C. | Lower |
| D. | None of these |
| Answer» D. None of these | |
| 8. |
For perfect intercooling in a two stage compressor |
| A. | p₂/p₁ = p₃/p₂ |
| B. | p₁/p₃ = p₂/p₁ |
| C. | p₁ = p3 |
| D. | p₁ = p₂ p3 |
| Answer» B. p₁/p₃ = p₂/p₁ | |
| 9. |
For perfect intercooling in a three stage compressor |
| A. | p₂/p₁ = p₃/p₂ = p₄/p₃ |
| B. | p₃/p₁ = p₄/p₂ |
| C. | p₁ p₂ = p₃ p₄ |
| D. | p₁ p₃ = p₂ p₄ |
| Answer» B. p₃/p₁ = p₄/p₂ | |
| 10. |
A closed cycle gas turbine gives ________ efficiency as compared to an open cycle gas turbine. |
| A. | Same |
| B. | Lower |
| C. | Higher |
| D. | None of these |
| Answer» D. None of these | |
| 11. |
The ratio of specific weight/h.p. of gas turbine and I.C engines may be typically of the order of |
| A. | 1: 1 |
| B. | 2: 1 |
| C. | 4: 1 |
| D. | 1: 6 |
| Answer» E. | |
| 12. |
The volumetric efficiency of a compressor |
| A. | Increases with decrease in compression ratio |
| B. | Decreases with decrease in compression ratio |
| C. | Increases with increase in compression ratio |
| D. | Decreases with increase in compression ratio |
| Answer» E. | |
| 13. |
A rocket works with maximum overall efficiency when air craft velocity is equal to the |
| A. | Jet velocity |
| B. | Twice the jet velocity |
| C. | Half the jet velocity |
| D. | Average of the jet velocity |
| Answer» D. Average of the jet velocity | |
| 14. |
If the flow of air through the compressor is perpendicular to its axis, then it is a |
| A. | Reciprocating compressor |
| B. | Centrifugal compressor |
| C. | Axial flow compressor |
| D. | Turbo compressor |
| Answer» C. Axial flow compressor | |
| 15. |
Atmospheric pressure is 1.03 kg/cm and vapour pressure is 0.03 kg/cm. The air pressure will be |
| A. | 1.03 kg/cm² |
| B. | 1.06 kg/cm² |
| C. | 1.00 kg/cm² |
| D. | 0.53 kg/cm² |
| Answer» D. 0.53 kg/cm² | |
| 16. |
The inter-cooler pressure, for minimum work required, for a two stage reciprocating air compressor, is given by (where p₁ = Intake pressure of air, p₂ = Inter-cooler pressure, and p₃ = Delivery pressure of air) |
| A. | p₂ = p₁ × p₃ |
| B. | p₂ = p₁/p₃ |
| C. | p₂ = p₁ × p₂ |
| D. | p₂ = p₃/p₁ |
| Answer» D. p₂ = p₃/p₁ | |
| 17. |
The volume of air delivered in a medium capacity air compressor per unit time is |
| A. | 0.1 to 1.2 m³/s |
| B. | 0.15 to 5 m³/s |
| C. | Above 5 m³/s |
| D. | None of these |
| Answer» C. Above 5 m³/s | |
| 18. |
A machine used to raise the pressure of air is called |
| A. | Gas turbine |
| B. | I.C engine |
| C. | Compressor |
| D. | Air motor |
| Answer» D. Air motor | |
| 19. |
The ratio of the discharge pressure to the inlet pressure of air is called |
| A. | Compression ratio |
| B. | Expansion ratio |
| C. | Compressor efficiency |
| D. | Volumetric efficiency |
| Answer» B. Expansion ratio | |
| 20. |
To avoid moisture troubles, the compressed air main line should |
| A. | Rise gradually towards the point of use |
| B. | Drop gradually towards the point of use |
| C. | Be laid vertically |
| D. | Be laid exactly horizontally |
| Answer» C. Be laid vertically | |
| 21. |
The air power of the compressor is also known as |
| A. | Indicated power |
| B. | Brake power |
| C. | Frictional power |
| D. | None of these |
| Answer» B. Brake power | |
| 22. |
In axial flow compressor, exit flow angle deviation from the blade angle is a function of |
| A. | Blade camber |
| B. | Blade camber and incidence angle |
| C. | Space-chord ratio |
| D. | Blade camber and space-chord ratio |
| Answer» C. Space-chord ratio | |
| 23. |
Reheating in a gas turbine |
| A. | Increases the thermal efficiency |
| B. | Increases the compressor work |
| C. | Increases the turbine work |
| D. | Decreases the thermal efficiency |
| Answer» B. Increases the compressor work | |
| 24. |
When air is to be compressed at a high pressure, then it is advantageous to use |
| A. | Single stage compression |
| B. | Multistage compression without intercooling |
| C. | Multistage compression with intercooling |
| D. | None of these |
| Answer» D. None of these | |
| 25. |
For speed above 3000 km/hour, it is more advantageous to use |
| A. | Turbojet engine |
| B. | Ramjet engine |
| C. | Propellers |
| D. | Rockets |
| Answer» C. Propellers | |
| 26. |
Which is false statement about air receivers? |
| A. | These are used to dampen pulsations |
| B. | These act as reservoir to take care of sudden demands |
| C. | These increase compressor efficiency |
| D. | These knock out some oil and moisture |
| Answer» D. These knock out some oil and moisture | |
| 27. |
In turbo fan engine, the jet velocity as compared to turbojet engine is |
| A. | Less |
| B. | More |
| C. | Same |
| D. | May be less or more depending upon speed |
| Answer» B. More | |
| 28. |
Reheating in multistage expansion gas turbine results in |
| A. | High thermal efficiency |
| B. | Reduction in compressor work |
| C. | Decrease of heat loss in exhaust |
| D. | Maximum work output |
| Answer» E. | |
| 29. |
Inter-cooling in gas turbine results in |
| A. | Increase in net output but decrease in thermal efficiency |
| B. | Increase in thermal efficiency but decrease in net output |
| C. | Increase in both thermal efficiency and net output |
| D. | Decrease in both thermal efficiency and net output |
| Answer» B. Increase in thermal efficiency but decrease in net output | |
| 30. |
If infinite number of heaters be used in a gas turbine, then expansion process in turbine approaches |
| A. | Isothermal |
| B. | Isentropic |
| C. | Adiabatic |
| D. | Isochoric |
| Answer» B. Isentropic | |
| 31. |
As the turbine inlet temperature increases, the thermal efficiency of gas turbine for the optimum pressure ratio |
| A. | Increases |
| B. | Decreases |
| C. | Remain same |
| D. | First increases and then decreases |
| Answer» B. Decreases | |
| 32. |
To avoid moisture troubles, the branch connections from compressed air lines should be taken from |
| A. | Top side of main |
| B. | Bottom side of main |
| C. | Left side of main |
| D. | Right side of main |
| Answer» B. Bottom side of main | |
| 33. |
Which of the following statement is correct as regard to centrifugal compressors? |
| A. | The flow of air is parallel to the axis of the compressor |
| B. | The static pressure of air in the impeller increases in order to provide centripetal force on the air |
| C. | The impeller rotates at high speeds |
| D. | The maximum efficiency is higher than multistage axial flow compressors |
| Answer» C. The impeller rotates at high speeds | |
| 34. |
Standard air is the air at ________ and relative humidity of 36 percent. |
| A. | 0.1 bar and 20°C |
| B. | 1 bar and 20°C |
| C. | 0.1 bar and 40°C |
| D. | 1 bar and 40°C |
| Answer» C. 0.1 bar and 40°C | |
| 35. |
Ram compression in turbojet involves |
| A. | Reduction of speed of incoming air and conversion of part of it into pressure energy |
| B. | Compression of inlet air |
| C. | Increasing speed of incoming air |
| D. | Lost work |
| Answer» B. Compression of inlet air | |
| 36. |
Which of the following fuels can be used in turbojet engines? |
| A. | Liquid hydrogen |
| B. | High speed diesel oil |
| C. | Kerosene |
| D. | Methyl alcohol |
| Answer» D. Methyl alcohol | |
| 37. |
The maximum combustion pressure in gas turbine as compared to I.C. engine is |
| A. | More |
| B. | Less |
| C. | Same |
| D. | Depends on other factors |
| Answer» C. Same | |
| 38. |
Mechanical efficiency of gas turbines as compared to I.C engines is |
| A. | Higher |
| B. | Lower |
| C. | Same |
| D. | None of the above |
| Answer» B. Lower | |
| 39. |
Separators in compressor installations are located |
| A. | Before inter-cooler |
| B. | After inter-cooler |
| C. | After receiver |
| D. | Between after-cooler and air receiver |
| Answer» E. | |
| 40. |
A rocket engine uses __________ for the combustion of its fuel. |
| A. | Surrounding air |
| B. | Compressed atmospheric air |
| C. | Its own oxygen |
| D. | None of these |
| Answer» D. None of these | |
| 41. |
If the flow of air through the compressor is parallel to its axis, then the compressor is |
| A. | Reciprocating compressor |
| B. | Centrifugal compressor |
| C. | Axial flow compressor |
| D. | Turbo compressor |
| Answer» D. Turbo compressor | |
| 42. |
The following is true for an open cycle gas turbine having exhaust heat exchanger. Atmospheric air before entering the compressor is |
| A. | Heated |
| B. | Compressed air before entering the combustion chamber is heated |
| C. | Bled gas from turbine is heated and readmitted for complete expansion |
| D. | Exhaust gases drive the compressor |
| Answer» C. Bled gas from turbine is heated and readmitted for complete expansion | |
| 43. |
Which is false statement about multistage compression? |
| A. | Power consumption per unit of air delivered is low |
| B. | Volumetric efficiency is high |
| C. | It is best suited for compression ratios around 7:1 |
| D. | The moisture in air is condensed in the inter-cooler |
| Answer» C. It is best suited for compression ratios around 7:1 | |
| 44. |
In a centrifugal compressor, an increase in speed at a given pressure ratio causes |
| A. | Increase in flow |
| B. | Decrease in flow |
| C. | Increase in efficiency |
| D. | Increase in flow and decrease in efficiency |
| Answer» E. | |
| 45. |
More than one stage will be preferred for reciprocating compressor if the delivery pressure is more than |
| A. | 2 kg/cm² |
| B. | 6 kg/cm² |
| C. | 10 kg/cm² |
| D. | 14.7 kg/cm² |
| Answer» B. 6 kg/cm² | |
| 46. |
The ratio of the volume of free air delivery per stroke to the swept volume of the piston, is known as |
| A. | Compressor efficiency |
| B. | Volumetric efficiency |
| C. | Isothermal efficiency |
| D. | Mechanical efficiency |
| Answer» C. Isothermal efficiency | |
| 47. |
A rocket engine for the combustion of its fuel |
| A. | Carries its own oxygen |
| B. | Uses surrounding air |
| C. | Uses compressed atmospheric air |
| D. | Does not require oxygen |
| Answer» B. Uses surrounding air | |
| 48. |
In an axial flow compressor, the ratio of pressure in the rotor blades to the pressure rise in the compressor in one stage is known as |
| A. | Work factor |
| B. | Slip factor |
| C. | Degree of reaction |
| D. | Pressure coefficient |
| Answer» D. Pressure coefficient | |
| 49. |
Which is false statement about advantages of multistage compressor in comparison to single stage compressor? |
| A. | Less power requirement |
| B. | Better mechanical balance |
| C. | Less loss of air due to leakage past the cylinder |
| D. | Lower volumetric efficiency |
| Answer» E. | |
| 50. |
For minimum work required to compress and deliver a quantity of air by multistage compression |
| A. | The compression ratio in each stage should be same |
| B. | The intercooling should be perfect |
| C. | The work-done in each stage should be same |
| D. | All of the above |
| Answer» E. | |