mechanical engineering MCQs – Page 173

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 Review each marked answer and report any item that may be outdated or unclear.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

3441. In locomotives, the draught is produced by_________________?
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A. chimney

B. induced draft fan

C. both combined A. and B.

D. steam jet draught

E. none of the above

3442. The bituminous coal is non-caking if its carbon content is_______________?
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A. 85-90%

B. 78-81%

C. 81-85%

D. 95-100%.

E. 90-95%

3443. Size of boiler tubes is specified by___________________?
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A. outside diameter and inside diameter

B. outside diameter and thickness

C. inside diameter and thickness

D. mean diameter and thickness

E. outside diameter alone

3444. The pressure of reheat steam after passing through reheater compared to inlet condition is _________________?
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A. equal

B. more

C. may be more or less depending on capacity of reheater

D. less

E. none of the above

3445. Green coal, in order to be burnt, must be____________________?
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A. burnt in excess air

B. burnt as lumps

C. heated to its ignition point

D. burnt as powder

E. heated sufficiently

3446. The basic job of feed water treatment in boilers is to overcome the problem of __________________?
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A. corrosion

B. carryover

C. scale

D. embrittlement

E. all of the above

3447. The diameter of fire tubes in Cochran boiler is of the order of___________________?
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A. 2 cm

B. 15 cm

C. 12 cm

D. 6 Cm ,

E. 8 cm

3448. The temperature of flue gases at air heater outlet should be__________________?
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A. 100C

B. above dew-point temperature of flue gases

C. above wet bulb temperature of flue gases

D. less than wet bulb temperature of flue gases

E. below dew-point temperature of flue gases

3449. Boiler H.P. is defined as the ________________ ?
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A. the evaporation of 15.65 kg of water per hour from and at 100C into dry saturated steam

B. heat consumed in evaporating 1 kg water at 0C to steam at 100C and 1.033 kg/cm pressure

C. steam evaporation rate per kg of fuel fired

D. work done by 1 kg of steam at saturation condition

E. work done in evaporating 1 kg of steam per hour from and at 100C into dry saturated steam

3450. The steam temperature with increase in load in case of a boiler fitted with radiation super heater________________?
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A. unpredictable

B. first increases and then decreases

C. decreases

D. increases

E. remains unaffected

3451. Natural water circulation, by convection in water tube boilers, with increase in pressure of boiler _________________?
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A. increases

B. decreases

C. first decreases and then increases

D. remains unaffected

E. first increases and then decreases

3452. The economizer is used in boilers to _______________________?
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A. extract heat from the exhaust flue gases

B. increase flue gas temperature

C. increase thermal efficiency of boiler

D. to heat feed water by bled steam

E. economise on fuel

3453. Bomb calorimeter is used to determine ___________________?
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A. Lower calorific value at constant volume ,

B. Lower calorific value at constant pressure

C. Higher calorific value at constant volume

D. Higher calorific value at constant pressure

E. None of the above

3454. In a throttling process________________?
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A. steam volume remains constant

B. steam pressure remains constant

C. steam entropy remains constant

D. steam temperature remaisn constant

E. steam enthalpy remains constant

3455. Calorific value of coal is of the order of _______________________?
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A. 8000-10,000 kcal/kg

B. 800-1200 kcal/kg

C. 200-400 kcal/kg

D. 5000-8000 kcal/kg

E. 2000-4000 kcal/kg

3456. Which is not the correct statement about moisture in coal ______________________?
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A. it increases thermal efficiency

B. inherent moisture and surface moisture are different things

C. in some coals moisture may be present upto 40%

D. moisture in coal is removed before firing by heating it with hot air

E. some moisture in coal helps in better burning which is not possible with completely dry coal

3457. Overfire burning is the phenomenon of _____________________?
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A. fuel bed firing

B. supply of excess, air

C. burning CO and unburnts in upper zone of furnace by supplying more air

D. supply of excess coal

E. none of the above

3458. Tertiary air is the air used to____________________?
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A. supply air for ignitors

B. cool the scanners

C. transport and dry the coal

D. provide air around burners for obtaining optimum combustion

E. convert CO (formed in lower zone of furnace) into C02 at higher zone

3459. Primary air is the air used to__________________?
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A. transport and dry the coal

B. convert CO (formed in lower zone of furnace) into C02 at higher zone

C. provide air around burners for obtaining optimum combustion

D. none ot the above

E. air-delivered by forced draft fan

3460. On Mollier chart, flow through turbine is represented by ________________?
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A. straight inclined line

B. horizontal straight line

C. none of the above

D. vertical straight line

E. curved line

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