mechanical engineering MCQs – Page 157

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 Review each marked answer and report any item that may be outdated or unclear.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

3121. The specific fuel consumption for a petrol engine first decreases with increase in fuel air ratio and then increases with further increase in fuel air ratio. The minimum value occurs in the range of__________________?
0

A. none of the above

B. lean mixture

C. chemically correct mixture

D. rich mixture

E. unpredictable

3122. In a typical medium speed, 4-stroke cycle diesel engine ___________________?
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A. fuel injection starts at top dead center and ends at 20 after top dead center

B. none of the above

C. fuel injection starts at just before top dead center and ends just after top deac center

D. fuelinjection starts at 10 before to dead center and ends at 20 after tor dead center

E. may start and end anywhere

3123. Pour point of fuel oil is the_________________?
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A. temperature at which it solidifies or congeals

B. minimum temperature to which oil is heated in order to give off inflammable vapours in sufficient quantity to ignite momentarily when brought in contact with a flame

C. temperature at which it flows easily

D. it catches fire without external aid

E. indicated by 90% distillation temperature i.e., when 90% of sample oil has distilled off

3124. Engine pistons are usually made of aluminium alloy because it_________________?
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A. is lighter

B. wears less

C. is stronger

D. absorbs shocks

E. does not react with fuel and lub oil

3125. Ignition quailty of petrol is expressed by___________________?
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A. distillation temperature

B. octane number

C. calorific value

D. cetane number

E. self ignition temperature

3126. The working cycle in case of four stroke engine is completed in following number of revolutions of crankshaft___________________?
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A. 4

B. 8

C. 2-Jan

D. 2

E. 1

3127. The following volume of air is required for consuming 1 liter of fuel by a four stroke engine_______________?
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A. 15-18 m3

B. 5 m3

C. 1 m3

D. 9-10 m3

E. 5-6 m3

3128. Violent sound pulsations within the cylinder of an I.C. engine are caused due to_________________?
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A. heavy turbulence

B. improved scavenging

C. preignition

D. detonation

E. heavy supercharging

3129. The m.e.p. of a diesel cycle having fixed compression ratio with increase in cut-off will_________________?
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A. increase

B. decreae

C. unpredictable

D. depend on other factors

E. be unaffected

3130. The inlet value of a four stroke cycle I.C engine remains open for nearly___________________?
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A. 200

B. 125

C. 235

D. 275

E. 180

3131. Hot air standard diesel cycle efficiency with increase in value of C_______________?
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A. unpredictable

B. increases

C. decreases

D. remains unaffected

E. depends on other factors

3132. Detonation can be controlled by_____________________?
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A. varying compression ratio

B. using lian mixture

C. retarding the spark timing

D. reducing the r.p.m.

E. increasing inlet pressure

3133. In petrol engines, advancing the spark timing will_______________?
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A. increase the knocking tendency

B. decrease the knocking tendency

C. increase or decrease knocking tendency depending on strenght and time of spark

D. not affect the knocking tendncy

E. unpredictable

3134. Which of the following engines can work on very lean mixture__________________?
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A. C.I. engine

B. S.I. engine

C. two stroke engine

D. four stroke engine

E. all of the above

3135. In carburettors, the top of the fuel jet with reference to the level in the float chamber is kept at_________________?
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A. may be anywhere

B. varies from situation to situation

C. slightly higher level

D. same level

E. slightly lower level

3136. The theoretically correct air fuel ratio for petrol engine is of the order of___________________?
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A. 20:01

B. 9:01

C. 6:01

D. 12:01

E. 15 : 1

3137. In petrol engines, the maximum power is developed corresponding to relative fuel air ratio of________________?
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A. 0.85

B. 1

C. 1.1 to 1.3

D. 1.2 to 1.5

3138. The actual volume of fresh charge admitted in 4-stroke petrol engine is_________________?
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A. equal to stroke volume

B. less than stroke volume

C. equal to stroke volume and clearance volume

D. more than stroke volume

E. more than cylinder volume

3139. Which is correct statement about reaction time for autoignition of fuel and the fuel air ratio__________________?
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A. non of the above

B. chemically correct mixture has mini-mum reaction time

C. rich mixture has high reaction time

D. all of the above

E. lean mixture has high reaction time

3140. The system of lubrication used for motor cycles and scooters is by________________?
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A. forced lubrication system

B. mixing about 5% lub oil with petrol

C. applying grease under pressure

D. wet sump method

E. splash lubrication

Showing 3121 to 3140 of 4266 mcqs