mechanical engineering MCQs – Page 158

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 Review each marked answer and report any item that may be outdated or unclear.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

3141. The thermal efficiency of a petrol engine of two stroke with crank case scavenging as compared to four stroke petrol engine with same comperssion ratio will be_____________________?
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A. depends on size of engine

B. same

C. higher

D. unpredictable.

E. lower

3142. The air-fuel ratio in petrol engines-is controlled by__________________?
0

A. carburettion

B. controlling valve opening/closing

C. scavenging and supercharging

D. injection

E. governing

3143. In the crankcase method of scavenging, the air pressure is produced by_________________?
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A. movement of engine piston

B. reciprocating pump

C. centrifugal pump

D. natural aspirator

E. supercharger

3144. In a diesel engine, the fuel is ignited by___________________?
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A. ignition

B. injected fuel

C. spark

D. heat resulting from compressing air that is supplied for combustion

E. combustion chamber

3145. The self-ignition temperature of diesel oil compared to petrol is_________________?
0

A. depends on quality of fuel

B. lower

C. higher

D. same

E. unpredictable

3146. Cetane___________________?
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A. has 100 cetane number

B. has zero cetane number

C. is a straight chain paraffin

D. determines the efficiency of an I.C. engine

E. helps detonation

3147. Solid injection in I.C. engines refers to injection of________________?
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A. liquid fuel only

B. solid fuel

C. does not exist

D. liquid fuel and air

E. solid fuel and air

3148. The termal efficiency of a petrol engine at design load is around_________________?
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A. 40%

B. 15%.

C. 50%

D. 30%

E. 90%

3149. Diesel engine can work on very lean air fuel ratio of the order of 30 : 1. A petrol engine can also work on such a lean ratio provided__________________?
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A. can not work as it is impossible

B. flywheel size is proper

C. it is properly designed

D. best quality fuel is used

E. engine cooling is stopped

3150. Cetane number is determined by comparing the performance of diesel oil with the following hydrocarbons___________________?
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A. ethylene dibromide

B. cetane

C. mixture of cetane with tetra-ethyl lead

D. mixture of aldehydes and ketones

E. mixture of cetane and alphamethyl napthalene

3151. Air injection in I.C. engines refers to injection of___________________?
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A. liquid fuel only

B. air only

C. does not exist

D. supercharging

E. liquid fuel and air

3152. Air fuel ratio at which a petrol engine can not work is_________________?
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A. 15:01

B. 10:01

C. 20 : 1 and less

D. will work at all ratios

E. 8:01

3153. The pour point of diesel oil must be_________________?
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A. lower than the coldest atmospheric temperature at which oil is to be pumped

B. has no such relation

C. more than 100C

D. higher than above

E. none of the above

3154. The delay period in petrol engine is of the order of__________________?
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A. 0.002 see

B. 0.01 sec

C. 0.001 sec

D. 0.05 sec

E. 0.1 sec

3155. The size of inlet valve of.an engine in comparison to exhaust valve is_________________?
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A. more

B. same

C. less

D. more/less depending on capacity of engine

E. varies from design to design

3156. Piston rings are usually made of___________________?
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A. cast iron

B. phosphor bronze

C. carbon steel

D. aluminium

E. babbitt

3157. Sulphur content in diesel oil should not be more than_________________?
0

A. 0.01%

B. 5%

C. 10%

D. 0.10%

E. 1%

3158. The specific fuel consumption per BH hour for a petrol engine is approximately__________________?
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A. 0.25 kg

B. 0.3kg

C. 0.35 kg

D. 0.15 kg

E. 0.2 kg

3159. Fuel oil consumption guarantees for I .C. engine are usually based on__________________?
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A. high heat value of oil

B. net calorific value of oil

C. all of the above

D. calorific value of fuel

E. low heat value of oil

3160. The term scavenging is generally associated with______________________?
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A. high efficiency engines

B. 4-stroke cycle engines

C. 2-stroke cycle engines

D. aeroplane engines

E. diesel engines

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