mechanical engineering MCQs – Page 163

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 Review each marked answer and report any item that may be outdated or unclear.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

3241. The thermal efficiecny of a diesel cycle having fixed compression ratio, with increase in cut-off ratio will___________________?
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A. may increase or decrease depending on other factors

B. be independent

C. none of the above

D. increase

E. decrease

3242. A diesel engine has_________________?
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A. 3 valves

B. 1 valve

C. 2 valves

D. no valve

E. 4 valves

3243. The magneto in an automobile is basically__________________?
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A. transformer

B. capacitor

C. a.c. generator

D. d.c. generator

E. magnetic circuit

3244. Which is more viscous lub oil_________________?
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A. SAE 80

B. SAE 4

C. SAE 50

D. SEA 30

E. SAE 70

3245. For the same power developed in I.C. engines, the cheaper system is_____________?
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A. supercharged

B. naturally aspirated

C. centrifugal pump

D. turbo charger

E. none of the above

3246. Pick up the wrong statement about supercharging __________________?
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A. supercharging is essential in aircraft engines

B. there can be limited supercharging in petrol engines because of detonation

C. supercharging reduces knocking in diesel engines

D. supercharging at high altitudes is essential

E. supercharging results in fuel economy

3247. In petrol engine, increase of cooling water temperature will_________________?
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A. unpredictable

B. increase or decrease knocking tendency depedning on strength and time of spark

C. not affect the knocking tendency

D. decrease the knocking tendecny

E. increase the knocking tendency

3248. If diesel is fed by mistake in the oil tank of a petrol engien, then engine will________________?
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A. knock

B. detonate

C. give lot of smoke

D. run for some time and then stop

E. not run

3249. The specific fuel consumption per BHP hour for diesel engine is approximately___________________?
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A. 0.25 kg

B. 0.2 kg

C. 0.15 kg

D. 0.3 kg

E. 0.35 kg

3250. The pressure and temperature at the end of compression stroke in a petrol engine are of the order of___________________?
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A. 6 12 kg/cm2 and 250 350C

B. 12 20 kg/cm2 and 350 450C

C. 20 30 kg/cm2 and 450 500C

D. 4 6 kg/cm2 and 200 250C

E. 30 40 kg/cm2 and 500 700C

3251. In a naturally aspirated diesel engine, the air is supplied by________________?
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A. a vacuum chamber

B. a supercharger

C. forced chamber

D. an injection tube

E. a centrifugal blower

3252. The spark plug gap is normally maintained at________________?
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A. 0.6 to 0.8 mm

B. 0.2 to 0.4 mm

C. 0.8 to 1 mm

D. 0.1 to 0.2 mm

E. 0.45 to 0.6 mm

3253. High carbon content in diesel oil used for diesel engine leads to_________________?
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A. production of highly corrosive gases corroding the cylinder walls and exhaust system

B. excessive engine wear

C. damaging of both the storage tank and the engine

D. deposition on engine parts

E. none of the above.

3254. Gaseous-fuel guarantees are based on___________________?
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A. high heat value of oil

B. low heat value of oil

C. calorific value of oil

D. mean heat value of oil

E. all of the above

3255. Injection lag is_________________?
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A. time corresponding to actual ignition and top dead center

B. the time taken by fuel after injection (before top dead center) to reach upto auto-ignition temperature

C. time corresponding to actual injection and top dead center

D. time before actual fuel injection and the pump pluger starts to pump fuel

E. none of the above

3256. Which of the following statements is correct ?
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A. All the irreversible engines have same efficiency

B. All the reversible engines have same efficiency

C. Both Rankine and Caront cycles have same efficiency between same temperature limits

D. All reversible engines working between same temperature limits have same-efficiency

E. Between same temperature limits, both petrol and diesel engines have same efficiency

3257. The knocking in diesel engines for given fuel, will be__________________?
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A. enhanced by increasing compression ratio

B. dependent on other factors

C. first enhanced by increasig compression ratio upto a limit beyond which it will be suppressed

D. enhanced by decreasing compression ratio

E. unaflected by compression ratio

3258. Does the supply of scavenging air at a density greater than that of atmosphere mean engine is supercharged ?
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A. depends on other factors

B. no

C. to some extent

D. unpredictable

E. yes

3259. Ignition quality of diesel-fuel oil is expressed by an index called__________________?
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A. octane number

B. calorific value

C. carbon content

D. ignition temperature

E. cetane number

3260. If overhead clearance is less, then the following type of engine should be selected__________________?
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A. Radial

B. Vertical

C. V-type

D. Horizontal

E. In-line

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