McqMate
These multiple-choice questions (MCQs) are designed to enhance your knowledge and understanding in the following areas: Mechanical Engineering .
Chapters
| 1. |
What is the correct formula for net work done of reciprocating engine? |
| A. | Wnet = mean effective pressure × clearance volume |
| B. | Wnet = mean effective pressure × total volume of cylinder |
| C. | Wnet = mean effective pressure × displacement volume |
| D. | none of the above |
| Answer» C. Wnet = mean effective pressure × displacement volume | |
| 2. |
Minimum work in compressor is possible when the value of adiabatic index n is equal to |
| A. | 0.75 |
| B. | 1 |
| C. | 1.27 |
| D. | 1.35 |
| Answer» B. 1 | |
| 3. |
Compressed air coming out from a punctured football |
| A. | becomes hotter |
| B. | becomes cooler |
| C. | remains at the same temperature |
| D. | may become hotter or cooler depending upon the humidity of the surrounding air |
| Answer» B. becomes cooler | |
| 4. |
The capacity of a compressor is 5 m /min. 5 m /min refers to |
| A. | standard air |
| B. | free air |
| C. | compressed air |
| D. | compressed air at delivery pressure |
| Answer» B. free air | |
| 5. |
The overall isothermal efficiency of compressor is defined as the ratio of |
| A. | isothermal h.p. to the BHP of motor |
| B. | isothermal h.p. to adiabatic h.p. |
| C. | power to drive compressor to isothermal h.p. |
| D. | work to compress air isothermally to work for actual compression |
| Answer» A. isothermal h.p. to the BHP of motor | |
| 6. |
The- most efficient method of compressing air is to compress it |
| A. | isothermally |
| B. | adiabatically |
| C. | isentropically |
| D. | isochronically |
| Answer» A. isothermally | |
| 7. |
Maximum work is done in compressing air when the compression is |
| A. | isothermal |
| B. | adiabatic |
| C. | polytropic |
| D. | any one of the above |
| Answer» B. adiabatic | |
| 8. |
The pressure and temperature conditions of air at the suction of compressor are |
| A. | pressure sightly less than atmospheric and temperature slightly more than atmospheric. |
| B. | slightly more than atmospheric |
| C. | slightly less than atmospheric |
| D. | pressure slightly more than atmospheric and temperature slightly less than atmospheric |
| Answer» A. pressure sightly less than atmospheric and temperature slightly more than atmospheric. | |
| 9. |
Isothermal compression effeicency can be attained by running the compressor |
| A. | at very high speed |
| B. | at very slow speed |
| C. | at average speed |
| D. | at zero speed |
| Answer» B. at very slow speed | |
| 10. |
The compressor capacity with decrease in suction temperature |
| A. | increases |
| B. | decreases |
| C. | remains unaffected |
| D. | may increase or decrease depending on compressor capacity |
| Answer» A. increases | |
| 11. |
Isothermal compression efficiency, even when running at high speed, can be approached by using |
| A. | multi-stage compression |
| B. | cold water spray |
| C. | both (a) and (b) above |
| D. | fully insulating the cylinder |
| Answer» C. both (a) and (b) above | |
| 12. |
Compression efficiency is compared against |
| A. | ideal compression |
| B. | adiabatic compression |
| C. | isothermal compression |
| D. | isentropic compression |
| Answer» C. isothermal compression | |
| 13. |
Aeroplanes employ following type of compressor |
| A. | radial flow |
| B. | axial flow |
| C. | centrifugal |
| D. | combination of above |
| Answer» B. axial flow | |
| 14. |
Inter cooling in compressors |
| A. | cools the delivered air |
| B. | results in saving of power in compressing a given volume to given pressure |
| C. | is the standard practice for big compressors |
| D. | enables compression in two stages |
| Answer» B. results in saving of power in compressing a given volume to given pressure | |
| 15. |
An ideal air compressor cycle without clearance on p-v diagram can be represented by following processes |
| A. | one adiabatic, two isobaric, and one constant volume |
| B. | two adiabatic and two isobaric |
| C. | two adiabatic, one isobaric and one constant volume |
| D. | one adiabatic, one isobaric and two constant volume |
| Answer» A. one adiabatic, two isobaric, and one constant volume | |
| 16. |
An ideal air compressor cycle with clearance on p-v diagram can be represented by following processes |
| A. | one adiabatic, two isobaric, and one constant volume |
| B. | two adiabatic and two isobaric |
| C. | two adiabatic, one isobaric and one constant volume, |
| D. | one adiabatic, one isobaric and two constant volume |
| Answer» B. two adiabatic and two isobaric | |
| 17. |
The work done per unit mass of air in compression will be least when n is equal to |
| A. | 1 |
| B. | 1.2 |
| C. | 1.3 |
| D. | 1.4 |
| Answer» A. 1 | |
| 18. |
Isothermal compression though most efficient, but is not -practicable because |
| A. | it requires very big cylinder |
| B. | it does not increase pressure much |
| C. | it is impossible in practice |
| D. | compressor has to run at very slow speed to achieve it |
| Answer» D. compressor has to run at very slow speed to achieve it | |
| 19. |
Ratio of indicated H.P. and brake H.P. is known as |
| A. | mechanical efficiency |
| B. | volumetric efficiency |
| C. | isothermal efficiency |
| D. | adiabatic efficiency |
| Answer» A. mechanical efficiency | |
| 20. |
The ratio of work doen per cycle to the swept volume in case of compressor is called |
| A. | compression index |
| B. | compression ratio |
| C. | compressor efficiency |
| D. | mean effective pressure |
| Answer» D. mean effective pressure | |
| 21. |
Cylinder clearance in a compressor should be |
| A. | as large as possible |
| B. | as small as possible |
| C. | about 50% of swept volume |
| D. | about 100% of swept volume |
| Answer» B. as small as possible | |
| 22. |
Ratio of compression is the ratio of |
| A. | gauge discharge pressure to the gauge intake pressure |
| B. | absolute discharge pressure to the absolute intake pressure |
| C. | pressures at discharge and suction corresponding to same temperature |
| D. | stroke volume and clearance volume |
| Answer» B. absolute discharge pressure to the absolute intake pressure | |
| 23. |
Clearance volume in actual reciprocating compressors is essential |
| A. | to accommodate Valves in the cylinder head |
| B. | to provide cushioning effect |
| C. | to attain high volumetric efficiency |
| D. | to provide cushioning effect and also to avoid mechanical bang of piston with cylinder head. |
| Answer» D. to provide cushioning effect and also to avoid mechanical bang of piston with cylinder head. | |
| 24. |
The net work input required for compressor with increase in clearance volume |
| A. | increases |
| B. | decreases |
| C. | remains same |
| D. | increases/decreases depending on compressor capacity |
| Answer» C. remains same | |
| 25. |
Ratio of indicated h.p. to shaft h.p. is known as |
| A. | compressor efficiency |
| B. | isothermal efficiency |
| C. | volumetric efficiency |
| D. | mechanical efficiency |
| Answer» D. mechanical efficiency | |
| 26. |
Volumetric efficiency is |
| A. | the ratio of stroke volume to clearance volume |
| B. | the ratio of the air actually delivered to the amount of piston displacement |
| C. | reciprocal of compression ratio |
| D. | index of compressor performance |
| Answer» B. the ratio of the air actually delivered to the amount of piston displacement | |
| 27. |
Volumetric efficiency of a compressor with clearance volume |
| A. | increases with increase in compression ratio |
| B. | decreases with increase in compression ratio |
| C. | is not dependent upon compression ratio |
| D. | may increase/decrease depending on compressor capacity |
| Answer» B. decreases with increase in compression ratio | |
| 28. |
Volumetric efficiency of a compressor without clearance volume |
| A. | increases with increase in compression ratio |
| B. | decreases with increase in compression ratio |
| C. | is not dependent upon compression ratio |
| D. | may increase/decrease depending on compressor capacity |
| Answer» C. is not dependent upon compression ratio | |
| 29. |
The clearance volume of the air compressor is kept minimum because |
| A. | it allows maximum compression to be achieved |
| B. | it greatly affects volumetric efficiency |
| C. | it results in minimum work |
| D. | it permits isothermal compression |
| Answer» B. it greatly affects volumetric efficiency | |
| 30. |
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 intercooler |
| Answer» B. Volumetric efficiency is high | |
| 31. |
Reciprocating air compressor is best suited for |
| A. | large quantity of air at high pressure |
| B. | small quantity of air at high pressure |
| C. | small quantity of air at low pressure |
| D. | large quantity of air at low pressure |
| Answer» B. small quantity of air at high pressure | |
| 32. |
Rotary compressor is best suited for |
| A. | large quantity of air at high pressure |
| B. | small quantity of air at high pressure |
| C. | small quantity of air at low pressure |
| D. | large quantity of air at low pressure |
| Answer» D. large quantity of air at low pressure | |
| 33. |
After-cooler is used to |
| A. | cool the air |
| B. | decrease the delivery temperature for ease in handling |
| C. | cause moisture and oil vapour to drop out |
| D. | reduce volume |
| Answer» C. cause moisture and oil vapour to drop out | |
| 34. |
The compressor performance at higher altitude compared to sea level will be |
| A. | same |
| B. | higher |
| C. | lower |
| D. | dependent on other factors |
| Answer» C. lower | |
| 35. |
Pick up the wrong statement about advantages of multistage compression |
| A. | better lubrication is possible advantages of multistage |
| B. | more loss of air due to leakage past the cylinder |
| C. | mechanical balance is better |
| D. | air can be cooled perfectly in between |
| Answer» B. more loss of air due to leakage past the cylinder | |
| 36. |
Losses in a centrifugal compressor are due to |
| A. | inlet losses |
| B. | impeller channel losses |
| C. | diffuser losses |
| D. | all of the above |
| Answer» D. all of the above | |
| 37. |
For supplying intermittent small quantity of air at high pressure, following compressor is best suited |
| A. | centrifugal |
| B. | reciprocating |
| C. | axial |
| D. | screw |
| Answer» B. reciprocating | |
| 38. |
For minimum work in multistage compression, assuming same index of compression in all stages |
| A. | work done in first stage should be more |
| B. | work done in subsequent stages should increase |
| C. | work done in subsequent stages should decrease |
| D. | work done in all stages should be equal |
| Answer» D. work done in all stages should be equal | |
| 39. |
Diffuser in a compressor is used to |
| A. | increase velocity |
| B. | make the flow stream-line |
| C. | convert pressure energy into kinetic energy |
| D. | convert kinetic energy into pressure energy |
| Answer» D. convert kinetic energy into pressure energy | |
| 40. |
Phenomenon of choking in compressor means |
| A. | no flow of air |
| B. | fixed mass flow rate regardless of pressure ratio |
| C. | reducing mass flow rate with increase in pressure ratio |
| D. | increased inclination of chord with air steam |
| Answer» B. fixed mass flow rate regardless of pressure ratio | |
| 41. |
Axial flow compressor has the following advantage over centrifugal compressor |
| A. | larger air handling ability per unit frontal area |
| B. | higher pressure ratio per stage |
| C. | aerofoil blades are used |
| D. | higher average velocities |
| Answer» A. larger air handling ability per unit frontal area | |
| 42. |
Rotary compressors are suitable for |
| A. | large discharge at high pressure |
| B. | low discharge at high pressure |
| C. | large discharge at low pressure |
| D. | low discharge at low pressure |
| Answer» C. large discharge at low pressure | |
| 43. |
The vloumetric efficiency of compressor with increase in compression ratio will |
| A. | increase |
| B. | decrease |
| C. | remain same |
| D. | may increase/decrease depending on clearance volume |
| Answer» B. decrease | |
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