mechanical engineering MCQs – Page 159

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 Review each marked answer and report any item that may be outdated or unclear.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

3161. Ignition timing of a multicylider petrol engine can be adjusted by_________________?
0

A. adjusting the spark plug gap

B. adjusting ignition coil position

C. rotating the distributor

D. delaying the spark by increasing capacitor in ignition circuit

E. rotating the crank

3162. A hmh flame speed is obtained in diesel engine when air fuel ratio is_______________?
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A. about 10% lean mixture

B. about 3-5% rich mixture

C. about 10% rich mixture

D. uniform throughout the mixture

E. chemically correct mixture

3163. The function of a fuel pump in a petrol pump is to______________________?
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A. inject fuel in cylinder

B. does not exist

C. supply fuel when carburettor fails

D. pump fuel so that it reaches carburettor (to improve thermal efficiency)

3164. Pick up the false statement ?
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A. S.I. engines are quality-governed engines

B. Theoretically correct mixture of air am petrol is approximately 15 : 1

C. High speed compression engines operate on dual combustion cycle

D. Diesel engines are compression ignition engines

E. Thermal efficiency of diesel engine i about 34%

3165. The efficiency of I.C. engines normally is of the order of_________________?
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A. 15-20%

B. 20-25%

C. 35-50%

D. 25-30%

E. 30-35%

3166. In isochronous governing, speed droop is_______________?
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A. 5%

B. 30%

C. 100%

D. 50%

E. 1%.

3167. Piston rings are plated with chromium,cadmium or phosphate in order to__________________?
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A. improve heat transfer

B. prevent clogging

C. improve surface finish

D. reduce wear and eliminate scuffing

E. reduce cost

3168. Octane number is determined by comparing the performance of the petrol with the following hydrocarbons__________________?
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A. iso-octane

B. alpha methyl napthalene

C. mixture of paraffins and aromatics

D. mixture of normal heptane and iso-oc-tane

E. mixture of methane and ethane

3169. The thermal efficiency of a diesel engine is of the order of_________________?
0

A. 92%

B. 68%

C. 25%.

D. 52%

E. 34%

3170. The most popular firing order in case of four cylinder in-line I.C. engine is__________________?
0

A. 1-2-3-4

B. 1-4-2-3

C. 1-3-4-

D. 1-2-4-3

E. 1-3-2-4

3171. The operation of forcing additional air under pressure in the engine cylinder is known as________________?
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A. scavenging

B. pre-ignition

C. dissociation and carburretion of fuel

D. supercharging

E. turbulence

3172. The calorific value of gaseous fuels is expressed in terms of__________________?
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A. kcal

B. kcal/m2

C. kcal/kg

D. all of the above

E. kcal/m

3173. Exhaust pipes of engines are covered with insulating marterial in order to_________________?
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A. conserve heat

B. reduce formation of condenstae

C. reduce heat transfer to the engine room

D. keep the exhaust pipes warm

E. increase engine efficiency

3174. In diesel engine the diesel fuel injected into cylinder would burn instantly at about compressed air temperature of____________________?
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A. 150CPC

B. 500C

C. 1000C

D. 250C

E. 2000C

3175. If one cylinder of a diesel engine receives more fuel than the others, then for that cylinder the________________?
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A. exhaust will be smoky

B. exhaust temperature will be high

C. engine starts overheating

D. scavenging occurs

E. piston rings would stick into piston grooves

3176. In loop scavenging, the top of the piston is________________?
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A. slanted

B. depressed

C. flat

D. contoured

E. convex shaped

3177. The maximum temperature in the I.C. engine cylinder is of the order of ________________?
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A. 1000- 1500C

B. 1500-2000C

C. 2000-2500C

D. 500- 1000C

E. 2500-3000C

3178. The specific gravity of diesel oil Is_________________?
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A. 0.7

B. 1.25

C. 0.5

D. 0.85

E. 1

3179. Freezing temperature of petrol is usually__________________?
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A. less than 30C

B. 0C

C. 10C

D. less than 273C

E. 10C

3180. Compression ratio of LC. engines is ___________________?
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A. cylinder volume/swept volume

B. the ratio of volumes of air in cylinder before compression stroke and after compression stroke

C. swept volume/cylinder volume

D. volume displaced by piston per stroke and clearance volume in cylinder

E. ratio of pressure after compression and before compression

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