1000+ Internal Combustion MCQ for RRB NTPC [Solved]

1. Iso-octane (C₈H₁₈) has octane number of
A. 0
B. 50
C. 100
D. 120
Answer : C

2. A two stroke cycle engine gives ________ the number of power strokes as compared to the four stroke cycle engine, at the same engine speed.
A. Half
B. Same
C. Double
D. Four times
Answer : C

3. The mechanical efficiency (?m) of the engine is given by
A. ?_m = B.P/I.P
B. ?_m = I.P/B.P
C. ?_m = (B.P × I.P)/100
D. None of these
Answer : A

4. Antiknock for compression ignition engines is
A. Napthene
B. Tetra ethyl lead
C. Amyl nitrate
D. Hexadecane
Answer : C

5. A diesel engine has compression ratio from
A. 6 to 10
B. 10 to 15
C. 15 to 25
D. 25 to 40
Answer : C

6. In diesel engine the diesel fuel injected into cylinder would burn instantly at about compressed air temperature of
A. 250°C
B. 500°C
C. 1000°C
D. 2000°C
Answer : C

7. The pressure at the end of compression in the case of diesel engine is of the order of
A. 6 kg/cm
B. 12 kg/cm
C. 20 kg/cm
D. 35 kg/cm
Answer : D

8. The inlet valve of a four stroke cycle internal combustion engine remains open for
A. 130°
B. 180°
C. 230°
D. 270°
Answer : C

9. In a four stroke cycle petrol engine, the compression
A. Starts at 40° after bottom dead centre and ends at 30° before top dead centre
B. Starts at 40° before bottom dead centre and ends at 30° after bottom dead centre
C. Starts at bottom dead centre and ends at top dead centre
D. May start and end anywhere
Answer : A

10. The size of inlet valve of an engine in comparison to exhaust valve is
A. More
B. Less
C. Same
D. More/less depending on capacity of engine
Answer : B

11. A supercharged engine as compared to an ordinary engine
A. Requires smaller foundation
B. Is lighter
C. Consumes less lubricating oil
D. All of these
Answer : D

12. The ratio of the indicated thermal efficiency to the air standard efficiency is known as
A. Mechanical efficiency
B. Overall efficiency
C. Volumetric efficiency
D. Relative efficiency
Answer : D

13. The exhaust valve in a four stroke cycle petrol engine
A. Opens at 50° before bottom dead centre and closes at 15° after top dead centre
B. Opens at bottom dead centre and closes at top dead centre
C. Opens at 50° after bottom dead centre and closes at 15° before top dead centre
D. May open and close anywhere
Answer : A

14. Which of the following medium is compressed in a Diesel engine cylinder?
A. Air alone
B. Air and fuel
C. Air and lub oil
D. Fuel alone
Answer : A

15. Installation of supercharger on a four cycle diesel engine can result in the following percentage increase in power
A. Up to 35%
B. Up to 50%
C. Up to 75%
D. Up to 100%
Answer : D

16. All heat engines utilize
A. Low heat value of oil
B. High heat value of oil
C. Net calorific value of oil
D. Calorific value of fuel
Answer : A

17. The output of a diesel engine can be increased without increasing the engine revolution or size in following way
A. Feeding more fuel
B. Heating incoming air
C. Scavenging
D. Supercharging
Answer : D

18. In a typical medium speed 4-stroke cycle diesel engines
A. Exhaust valve opens at 35° before bottom dead centre and closes at 20° after top dead centre
B. Exhaust valve opens at bottom dead centre and closes at top dead centre
C. Exhaust valve opens just after bottom dead centre and closes just before top dead centre
D. May open and close anywhere
Answer : A

19. The reference fuels for knock rating of spark ignition engines would include
A. Iso-octane and alpha-methyl naphthalene
B. Normal octane and aniline
C. Isooctane and normal hexane
D. Normal heptane and isooctane
Answer : D

20. Theoretically, a four stroke cycle engine should develop _________ power as that of a two stroke cycle engine.
A. Half
B. Same
C. Double
D. Four times
Answer : A

21. Supercharging is the process of
A. Supplying the intake of an engine with air at a density greater than the density of the surrounding atmosphere
B. Providing forced cooling air
C. Injecting excess fuel for raising more loads
D. Supplying compressed air to remove combustion products fully
Answer : A

22. Pour point of fuel oil is the
A. 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
B. Temperature at which it solidifies or congeals
C. It catches fire without external aid
D. Indicated by 90% distillation temperature i.e., when 90% of sample oil has distilled off
Answer : B

23. A gas engine has a swept volume of 300 cm3 and clearance volume of 25 cm3. Its volumetric efficiency is 0.88 and mechanical efficiency is 0.90. The volume of the mixture taken in per stroke is
A. 248 cm³
B. 252 cm³
C. 264 cm³
D. 286 cm³
Answer : C

24. The function of a distributor in a coil ignition system of I.C. engines is
A. To distribute spark
B. To distribute power
C. To distribute current
D. To time the spark
Answer : D

25. The volumetric efficiency of a well designed engine may be
A. 30 to 40 %
B. 40 to 60 %
C. 60 to 70 %
D. 75 to 90 %
Answer : D

26. In a four stroke cycle petrol engine, the inlet valve
A. Opens at top dead centre and closes at bottom dead centre
B. Opens at 20° before top dead centre and closes at 40° after bottom dead centre
C. Opens at 20° after top dead centre and closes at 20° before bottom dead centre
D. May open or close anywhere
Answer : B

27. The theoretically correct air fuel ratio for petrol engine is of the order of
A. 6 : 1
B. 9 : 1
C. 12 : 1
D. 15 : 1
Answer : D

28. The actual volume of fresh charge admitted in 4-stroke petrol engine is
A. Equal to stroke volume
B. Equal to stroke volume and clearance volume
C. Less than stroke volume
D. More than stroke volume
Answer : C

29. The reason for supercharging in any engine is to
A. Increase efficiency
B. Increase power
C. Reduce weight and bulk for a given output
D. Effect fuel economy
Answer : C

30. Morse test is used to determine the I.P. of a
A. Single cylinder petrol engine
B. Four stroke engine
C. Single cylinder diesel engine
D. Multi cylinder engine
Answer : D

31. The process of breaking up or a liquid into fine droplets by spraying is called
A. Vaporisation
B. Carburetion
C. Ionisation
D. Atomisation
Answer : D

32. Does the supply of scavenging air at a density greater than that of atmosphere mean engine is supercharged?
A. Yes
B. No
C. To some extent
D. Unpredictable
Answer : B

33. Crankcase explosion in I.C. engines usually occurs as
A. First a mild explosion followed by a bi explosion
B. First a big explosion followed by a mil explosion
C. Both mild and big explosions occurs simultaneously
D. Never occurs
Answer : A

34. Stoichiometric ratio is
A. Chemically correct air-fuel ratio by weight
B. Chemically correct air-fuel ratio by volume
C. Actual air-fuel ratio for maximum efficiency
D. None of the above
Answer : B

35. In a petrol engine, the mixture has the lowest pressure at the
A. Beginning of suction stroke
B. End of suction stroke
C. End of compression stroke
D. None of these
Answer : B

36. In a four stroke cycle diesel engine, the compression
A. Starts at 40° after bottom dead centre and ends at 10° before top dead centre
B. Starts at 40° before top dead centre and ends at 40° after top dead centre
C. Starts at top dead centre and ends at 40° before bottom dead centre
D. May start and end anywhere
Answer : A

37. The spark ignition engines are governed by
A. Hit and miss governing
B. Qualitative governing
C. Quantitative governing
D. Combination of (B) and (C)
Answer : C

38. The thermal efficiency of a standard Otto cycle for a compression ratio of 5.5 will be
A. 25 %
B. 50 %
C. 70 %
D. 100 %
Answer : B

39. If the compression ratio in I.C. engine increases, then its thermal efficiency will
A. Decrease
B. Increase
C. Remain same
D. None of these
Answer : B

40. The increase of efficiency of a compression ignition engine, as the load decreases, is due to
A. Higher maximum temperature
B. Qualitative governing
C. Quantitative governing
D. Hit and miss governing
Answer : B

41. In compression ignition engines, swirl denotes a
A. Haphazard motion of the gases in the chamber
B. Rotary motion of the gases in the chamber
C. Radial motion of the gases in the chamber
D. None of the above
Answer : B

42. The specific fuel consumption per BH hour for a petrol engine is approximately
A. 0.15 kg
B. 0.2 kg
C. 0.25 kg
D. 0.3 kg
Answer : C

43. The object of providing masked inlet valve in the air passage of compression ignition engines is to
A. Enhance flow rate
B. Control air flow
C. Induce primary swirl
D. Induce secondary turbulence
Answer : C

44. The advancing of spark timing in spark ignition engines will _________ knocking tendency.
A. Increase
B. Reduce
C. Not effect
D. None of these
Answer : A

45. The air requirement of a petrol engine during starting compared to theoretical air required for complete combustion is
A. More
B. Less
C. Same
D. May be more or less depending on engine capacity
Answer : B

46. Scavenging is usually done to increase
A. Thermal efficiency
B. Speed
C. Power output
D. Fuel consumption
Answer : C

47. Which one of the following event would reduce volumetric efficiency of a vertical compression ignition engine?
A. Inlet valve closing after bottom dead centre
B. Inlet valve closing before bottom dead centre
C. Inlet valve opening before top dead centre
D. Exhaust valve closing after top dead centre
Answer : B

48. The ratio of the volume of charge admitted at N.T.P. to the swept volume of the piston is called
A. Mechanical efficiency
B. Overall efficiency
C. Volumetric efficiency
D. Relative efficiency
Answer : C

49. Which of the following does not relate to a compression ignition engine?
A. Fuel pump
B. Fuel injector
C. Governor
D. Carburettor
Answer : D

50. Detonation is harmful due to
A. Increase in the rate of heat transfer, there is a reduction in the power output and efficiency of the engine
B. Excessive turbulence which removes most of the insulating gas boundary layer from the cylinder walls
C. High intensity of knock causes crankshaft vibration and the engine runs rough
D. None of the above
Answer : D