mechanical engineering MCQs – Page 116

Practise multiple-choice questions from mechanical engineering for competitive examinations and subject revision. Review each marked answer and report any item that may be outdated or unclear.

mechanical engineering Mcqs

1. compressors gas turbines and jet engines 2. theory of machines 3. nuclear power plants 4. engineering materials 5. strength of materials mechanical engineering 6. thermodynamics 7. heat transfer 8. i c engines 9. steam boilers engines nozzles and turbines 10. engineering mechanics 11. fluid mechanics mechanical engineering 12. production technology 13. machine design 14. hydraulic machines 15. workshop technology 16. refrigeration and air conditioning

2301. Atmospheric pressure is 1.03 kg/cm and vapour pressure is 0.03 kg/cm . The air pressure will be_____________________ ?
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A. 0.5 kg/cm2

B. 1.06 kg/cm2

C. 1.03 kg/cm2

D. 0.53 kg/cm2

E. 1.00 kg/cm2

2302. Mechanical efficiency of gas turbines as compared to I.C engines is____________________?
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A. depends on on odier considerations

B. same

C. higher

D. lower

E. unpredictable

2303. Inter cooling in compressors__________________?
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A. enables compression in two stages

B. prevents compressor jacket running very hot

C. results in saving of power in compressing a given volume to given pressure

D. cools the delivered air

E. is the standard practice for big compressors

2304. Propulsion efficiency of the following order-is obtained in practice _______________?
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A. 60%

B. 72%

C. 85%.

D. 34%

E. 50%

2305. The combustion efficiency of a gas turbine using perfect combustion chamber is of the order of________________?
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A. 75%

B. 99%

C. 85%

D. 50%

E. 90%

2306. Efficiency of gas turbine is increased by________________ ?
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A. reheating

B. all of the above

C. inter cooling

D. none of the above

E. adding a regenerator

2307. The work ratio of simple gas turbine cycle depends on_________________?
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A. maximum cycle temperature

B. minimum cycle temperature

C. pressure ratio

D. all of the above

E. none of die above

2308. Surging phenomenon in centrifugal com-pressor depends on ___________________?
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A. k up wrong statement ?

B. stagnation pressure at the outlet

C. pressure ratio

D. change in load

E. all of the above

F. mass flow rate

2309. Open cycle gas turbine works on___________________?
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A. Brayton or Atkinson cycle

B. ankine cycle

C. Carnot cycle

D. Joule cycle

E. Erricsson cycle

2310. An ideal air compressor cycle with clearance on p-v diagram can be represented by following processes_______________?
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A. two adiabatic, one isobaric and one constant volume,

B. two adiabatic and two isobaric

C. two isobaric, two adiabatic and one constant volume

D. one adiabatic, one isobaric and two constant volume

E. one adiabatic, two isobaric, and one constant volume

2311. The thermodynamic efficiency of rotary compressor is based on_______________?
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A. none of the above

B. polytropic compression

C. isentropic compression

D. adiabatic compression

E. isothermal compression

2312. Maximum temprature in a gas turbine is of the order of COMPRESSORS, GAS TURBINES AND JET ENGINES______________________?
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A. 1500C

B. 700C

C. 2000C

D. 1000C

E. 2500C

2313. Ratio of indicated h.p. to shaft h.p. in known as__________________?
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A. adiabatic efficiency

B. mechanical efficiency

C. volumetric efficiency

D. compressor efficiency

E. isothermal efficiency

2314. Phenomenon of choking in compressor means __________________?
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A. no flow of air

B. does not occur

C. reducing mass flow rate with increase in pressure ratio

D. fixed mass flow rate regardless of pressure ratio

E. increased inclination of chord with air steam

2315. 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 E. high stroke_________________?
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A. thermal compression efficiency, even when running at high speed, can be approached by using

B. multi-stage compression

C. cold water spray

D. both A. and B. above

E. fully insulating the cylinder

F. high stroke

2316. Pick up the wrong statement ?
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A. axial flow compressors apt to be longer as compared to centrifugal type

B. Axial flow compressors have a sub-stantially constant delivery at variable pressures

C. centrifugal compressors have a wider stable operating range than axial flow compressors

D. centrifugal compressors deliver prac-tically constant pressure over a considerable range of capacities

E. axial flow compressors are bigger in diameter compared to centrifugal type

2317. In jet engines, paraffin is usually used as the fuel because of its _________________?
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A. A. and C. above

B. low freezing point

C. ease of atomisation

D. high calorific value

E. none of the above

2318. The ratio of isentropic work to eulers work is known as _____________________?
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A. pressure ratio

B. Eulers efficiency

C. isentropic efficiency

D. compressor efficiency

E. pressure coefficient

2319. The maximum propulsion efficiency of a turbojet is attained at around following speed __________________?
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A. 4000 km/hr

B. 1050km/hr

C. 550 km/hr

D. 1700 km/hr

E. 2400km /hr

2320. Typewriter constitutes__________________?
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A. machine

B. none of the above

C. mechanism

D. inversion

E. structure

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