1000+ Internal Combustion Multiple Choice Question Answer [Solved]

1. In a typical medium speed 4-stroke cycle diesel engine the inlet valve
A. Opens at 20° before top dead center and closes at 35° after the bottom dead center
B. Opens at top dead center and closes at bottom dead center
C. Opens at 10° after top dead center and closes 20° before the bottom dead center
D. May open or close anywhere
Answer : A

2. The thermodynamic cycle on which the petrol engine works, is
A. Otto cycle
B. Joule cycle
C. Rankine cycle
D. Stirling cycle
Answer : A

3. Which of the following is not an interns combustion engine?
A. 2-stroke petrol engine
B. 4-stroke petrol engine
C. Diesel engine
D. Steam turbine
Answer : D

4. The cetane number of diesel oil, generally available, is
A. 20 to 25
B. 25 to 30
C. 30 to 40
D. 40 to 55
Answer : D

5. In a four stroke cycle petrol engine, the expansion
A. Starts at top dead centre and ends at bottom dead centre
B. Starts at 30° before top dead centre and ends at 50° before bottom dead centre
C. Starts at 30° after top dead centre and ends at 50° after bottom dead centre
D. May start and end anywhere
Answer : B

6. In the opposed piston diesel engine, the combustion chamber is located
A. Above the piston
B. Below the piston
C. Between the pistons
D. There is no such criterion
Answer : C

7. The minimum cranking speed in case of petrol engine is about
A. Half the operating speed
B. One fourth of operating speed
C. 250 - 300 rpm
D. 60 - 80 rpm
Answer : D

8. 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

9. The air standard efficiency of an I.C. engine is given by (where r = Compression ratio, and ? = Ratio of specific heats)
A. 1 - r^{? - 1}
B. 1 + r^{? - 1}
C. 1 - (1/r^{? - 1})
D. None of these
Answer : C

10. Diesel as compared to petrol is
A. Highly ignitable
B. More difficult to ignite
C. Less difficult to ignite
D. None of these
Answer : B

11. The specific fuel consumption per B.P. hour for a diesel engine is about
A. 0.2 kg
B. 0.25 kg
C. 0.3 kg
D. 0.35 kg
Answer : A

12. Compression loss in I.C engines occurs due to
A. Leaking piston rings
B. Use of thick head gasket
C. Clogged air inlet slots
D. All of the above
Answer : D

13. In the crankcase method of scavenging, the air pressure is produced by
A. Supercharger
B. Centrifugal pump
C. Natural aspirator
D. Movement of engine piston
Answer : D

14. In an internal combustion engine, the process of removing the burnt gases from the combustion chamber of the engine cylinder is known as
A. Scavenging
B. Detonation
C. Supercharging
D. Polymerisation
Answer : A

15. Engine pistons are usually made of aluminium alloy because it
A. Is lighter
B. Wear is less
C. Absorbs shocks
D. Is stronger
Answer : A

16. 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

17. Which of the following statements is correct?
A. All the irreversible engines have same efficiency
B. All the reversible engines have same efficiency
C. Both Rankine and Carnot cycles have same efficiency between same temperature limits
D. All reversible engines working between same temperature limits have same efficiency
Answer : D

18. A fuel of an octane number rating of 75 matches in knocking intensity as a mixture of
A. 75% iso-octane and 25% normal heptane
B. 75% normal heptane and 25% iso-octane
C. 75% petrol and 25% diesel
D. 75% diesel and 25% petrol
Answer : A

19. The air-fuel ratio of the petrol engine is controlled by
A. Carburettor
B. Injector
C. Governor
D. None of these
Answer : A

20. Which of the following fuel has little tendency towards detonation?
A. Benzene
B. Iso-octane
C. Normal heptane
D. Alcohol
Answer : B

21. The knocking tendency in compression ignition engines for a given fuel will be
A. Enhanced by decreasing compression ratio
B. Enhanced by increasing compression ratio
C. Dependent on other factors
D. None of the above
Answer : A

22. The specific fuel consumption per B.P. hour for a petrol engine is about
A. 0.2 kg
B. 0.25 kg
C. 03 kg
D. 0.35 kg
Answer : B

23. Thermal efficiency of a two stroke cycle engine is ________ a four stroke cycle engine.
A. Equal to
B. Less than
C. Greater than
D. None of these
Answer : B

24. The accumulation of carbon in a cylinder results in increase of
A. Clearance volume
B. Volumetric efficiency
C. Ignition time
D. Effective compression ratio
Answer : D

25. The injector nozzle of a compression ignition engine is required to inject fuel at a sufficiently high pressure in order to
A. Inject fuel in a chamber of high pressure at the end of compression stroke
B. Inject fuel at a high velocity to facilitate atomisation
C. Ensure that penetration is not high
D. All of the above
Answer : D

26. 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

27. A diesel engine, during suction stroke, draws
A. Air only
B. Diesel only
C. A mixture of diesel and air
D. None of these
Answer : A

28. The sensing element in the control system of nuclear reactors measures the _________ of the neutron flux in the reactor.
A. Temperature
B. Volume
C. Density
D. None of these
Answer : C

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

30. Which of the following is the lightest and most volatile liquid fuel?
A. Diesel
B. Kerosene
C. Fuel oil
D. Gasoline
Answer : D

31. 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

32. The specific fuel consumption of a petrol engine compared to diesel engine of same H.P. is
A. Same
B. More
C. Less
D. Less or more depending on operating conditions
Answer : B

33. The thermal efficiency of diesel engines on weak mixtures is
A. Unaffected
B. Lower
C. Higher
D. Dependent on other factors
Answer : C

34. If the compression ratio of an engine working on Otto cycle is increased from 5 to 7, the percentage increase in efficiency will be
A. 2 %
B. 4 %
C. 8 %
D. 14 %
Answer : D

35. The working pressure and temperature inside the cylinder of an internal combustion engine is _________ as compared to a steam engine.
A. Low
B. Very low
C. High
D. Very high
Answer : D

36. If one cylinder of a diesel engine receives more fuel than the others, then for that cylinder the
A. Exhaust will be smoky
B. Piston rings would stick into piston grooves
C. Engine starts overheating
D. Scavenging occurs
Answer : D

37. In a four stroke cycle, the minimum temperature inside the engine cylinder occurs at the
A. Beginning of suction stroke
B. End of suction stroke
C. Beginning of exhaust stroke
D. End of exhaust stroke
Answer : A

38. Pick up the wrong statement about supercharging
A. Supercharging reduces knocking in diesel engines
B. There can be limited supercharging in petrol engines because of detonation
C. Supercharging at high altitudes is essential
D. Supercharging results in fuel economy
Answer : D

39. Combustion in compression ignition engines is
A. Homogeneous
B. Heterogeneous
C. Both (A) and (B)
D. Laminar
Answer : B

40. Supercharging is the process of supplying the intake air to the engine cylinder at a density _________ the density of the surrounding atmosphere.
A. Equal to
B. Less than
C. Greater than
D. None of these
Answer : C

41. The effective inhibitor of pre-ignition is
A. Alcohol
B. Water
C. Lead
D. None of these
Answer : B

42. Alpha-methyl-naphthalene (C?? H??) has a cetane number of
A. 0
B. 50
C. 100
D. 120
Answer : A

43. 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

44. In loop scavenging, the top of the piston is
A. Flat
B. Contoured
C. Slanted
D. Depressed
Answer : B

45. If the temperature of intake air in internal combustion engine increases, then its efficiency will
A. Remain same
B. Decrease
C. Increase
D. None of these
Answer : B

46. The calorific value of gaseous fuels is expressed in terms of
A. kcal
B. kcal/kg
C. kcal/m²
D. kcal/m³
Answer : D

47. The working cycle in case of four stroke engine is completed in following number of revolutions of crankshaft
A. 1/2
B. 1
C. 2
D. 4
Answer : C

48. The method of determination of indicated power of a multi cylinder spark ignition engine is by the use of
A. Morse test
B. Prony brake test
C. Motoring test
D. Heat balance test
Answer : A

49. The ratio of indicated thermal efficiency to the corresponding air standard cycle efficiency is called
A. Net efficiency
B. Efficiency ratio
C. Relative efficiency
D. Overall efficiency
Answer : C

50. 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