1000+ Internal Combustion Multiple Choice Question Answer [Solved]

1. 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

2. The fuel valve in a four stroke cycle diesel engine
A. Opens at 15° after top dead centre and closes at 20° before bottom dead centre
B. Opens at 15° before top dead centre and closes at 20° after top dead centre
C. Opens at top dead centre and closes at bottom dead centre
D. May open and close anywhere
Answer : B

3. 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

4. The self ignition temperature of petrol is ________ as compared to diesel oil.
A. Same
B. Lower
C. Higher
D. None of these
Answer : C

5. The air standard efficiency of an I.C. engine depends on
A. Fuel used
B. Speed of engine
C. Compression ratio
D. None of these
Answer : C

6. Which of the following statement is correct?
A. Compression ratio for petrol engines varies from 6 to 10
B. Higher compression ratio in diesel engines results in higher pressures
C. Petrol engines work on Otto cycle
D. All of the above
Answer : D

7. The knocking in spark ignition engines can be reduced by
A. Retarding the spark
B. Increasing the engine speed
C. Both (A) and (B)
D. None of these
Answer : C

8. If the intake air temperature of I.C. engine increases, its efficiency will
A. Increase
B. Decrease
C. Remain same
D. None of these
Answer : B

9. A 5 BHP engine running at full load would consume diesel of the order of
A. 0.3 kg/hr
B. 1 kg/hr
C. 3 kg/hr
D. 5 kg/hr
Answer : B

10. 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

11. In diesel engine, the compression ratio in comparison to expansion ratio is
A. Same
B. Less
C. More
D. Variable
Answer : C

12. 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

13. 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

14. Air fuel ratio for idling speed of a petrol engine is approximately
A. 1 : 1
B. 5 : 1
C. 10 : 1
D. 15 : 1
Answer : C

15. 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

16. 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

17. The following volume of air is required for consuming 1 litre of fuel by a four stroke engine
A. 1 m3
B. 5 m3
C. 56 m3
D. 910 m3
Answer : D

18. The cetane (C₁₆H₃₄) which is a straight chain paraffin, is assigned a cetane number of
A. 0
B. 50
C. 100
D. 120
Answer : C

19. By higher octane number of spark ignition fuel, it is meant that the fuel has
A. Higher heating value
B. Higher flash point
C. Lower volatility
D. Longer ignition delay
Answer : D

20. The combustion in compression ignition engines is
A. Homogeneous
B. Heterogeneous
C. Both (A) and (B)
D. None of these
Answer : B

21. In a petrol engine, if diesel is used, then the engine will
A. Not run
B. Run more efficiently
C. Run at high speed
D. Explode
Answer : A

22. The term scavenging is generally associated with
A. 2-stroke cycle engines
B. 4-stroke cycle engines
C. Aeroplane engines
D. High efficiency engines
Answer : D

23. High speed compression engines operate on
A. Otto cycle
B. Diesel cycle
C. Dual combustion cycle
D. All of these
Answer : C

24. The fuel in diesel engine is normally injected at pressure of
A. 5-10 kg/cm²
B. 20-25 kg/cm²
C. 60-80 kg/cm²
D. 90-130 kg/cm²
Answer : D

25. In petrol engines, the delay period is of the order of
A. 0.001 second
B. 0.002 second
C. 0.003 second
D. 0.004 second
Answer : B

26. Which of the following statement is correct regarding petrol engines?
A. A fine fuel spray mixed with air is ignited by the heat of compression which is at a high pressure
B. The fuel supplied to the engine cylinder is mixed with necessary amount of air and the mixture in ignited with the help of a spark plug
C. The fuel is first evaporated after passing through a carburettor and is mixed with air before ignition
D. All of the above
Answer : B

27. 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

28. 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

29. 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

30. 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

31. The theoretically correct mixture of air and petrol is
A. 10 : 1
B. 15 : 1
C. 20 : 1
D. 25 : 1
Answer : B

32. A spark plug gap is kept from
A. 0.3 to 0.7 mm
B. 0.2 to 0.8 mm
C. 0.4 to 0.9 mm
D. 0.6 to 1.0 mm
Answer : A

33. A carburettor is used to supply
A. Petrol, air and lubricating oil
B. Air and diesel
C. Petrol and lubricating oil
D. Petrol and air
Answer : D

34. 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

35. 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

36. 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

37. 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

38. The reflectivity depends upon
A. Geometry of the reflector
B. Energy of neutrons
C. Properties of the reflector
D. All of these
Answer : D

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

40. The thermal efficiency of petrol and gas engines is about
A. 15 %
B. 30 %
C. 50 %
D. 70 %
Answer : B

41. 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

42. The ignition quality of diesel oil is expressed by
A. Cetane number
B. Octane number
C. Calorific value
D. None of these
Answer : A

43. 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

44. 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

45. Diesel fuel, compared to petrol is
A. Less difficult to ignite
B. Just about the same difficult to ignite
C. More difficult to ignite
D. Highly ignitable
Answer : C

46. Scavenging air in diesel engine means
A. Air used for combustion sent under pressure
B. Forced air for cooling cylinder
C. Burnt air containing products of combustion
D. Air used for forcing burnt gases out of engine's cylinder during the exhaust period
Answer : D

47. The magneto in an automobile is basically
A. Transformer
B. D.C. generator
C. Capacitor
D. Magnetic circuit
Answer : B

48. The ignition quality of petrol is expressed by
A. Cetane number
B. Octane number
C. Calorific value
D. All of these
Answer : B

49. Fuel consumption of diesel engines is not guaranteed at one quarter load because at such low loads
A. The friction is high
B. The friction is unpredictable
C. The small difference in cooling water temperature or in internal friction has a disproportionate effect
D. The engine is rarely operated
Answer : C

50. Which of the following statement is wrong?
A. In compression ignition engines, detonation occurs near the beginning of combustion.
B. Since the fuel, in compression ignition engines, is injected at the end of compression stroke, therefore, there will be no pre-ignition.
C. To eliminate knock in compression ignition engines, we want to achieve auto-ignition not early and desire a long delay period.
D. In compression ignition engines, because of heterogeneous mixture, the rate of pressure rise is comparatively lower.
Answer : C