1000+ Internal Combustion MCQ for LIC AAO [Solved]

1. In a diesel engine, the fuel is ignited by
A. Spark
B. Injected fuel
C. Heat resulting from compressing air that is supplied for combustion
D. Ignition
Answer : C

2. Which of the following fuel detonates readily?
A. Benzene
B. Iso-octane
C. Normal heptane
D. Alcohol
Answer : C

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

4. 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

5. The firing order in an I.C. engine depends upon
A. Arrangement of the cylinders
B. Design of crankshaft
C. Number of cylinders
D. All of these
Answer : D

6. The increase in intake temperature of internal combustion engines will _________ efficiency.
A. Have no effect on
B. Increase
C. Decrease
D. None of these
Answer : C

7. 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

8. 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

9. The delay period in compression ignition engines depends upon
A. Temperature and pressure in the cylinder at the time of injection
B. Nature of the fuel mixture strength
C. Relative velocity between the fuel injection and air turbulence pressure of residual gases
D. All of the above
Answer : D

10. 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

11. 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

12. 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

13. If V? is the jet velocity and V? is the vehicle velocity, then propulsive efficiency of a turbojet engine is
A. V?/(V? + V?)
B. V?/(V? + V?)
C. 2V?/(V? + V?)
D. 2V?/(V? + V?)
Answer : C

14. If petrol is used in a diesel engine, then
A. Low power will be produced
B. Efficiency will be low
C. Higher knocking will occur
D. Black smoke will be produced
Answer : C

15. 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

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

17. An engine indicator is used to determine the following
A. Speed
B. Temperature
C. Volume of cylinder
D. m.e.p. and I.H.P.
Answer : D

18. 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

19. The knocking tendency in spark ignition engines may be decreased by
A. Controlling the air-fuel mixture
B. Controlling the ignition timing
C. Controlling the exhaust temperature
D. Reducing the compression ratio
Answer : D

20. For maximum power generation, the air fuel ratio for a petrol engine for vehicles, is of the order of
A. 9 : 1
B. 12 : 1
C. 15 : 1
D. 18 : 1
Answer : B

21. 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

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

23. 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

24. The higher combustion chamber wall temperature in compression ignition engines will _________ knocking tendency.
A. Increase
B. Reduce
C. Not effect
D. None of these
Answer : B

25. Which of the following is false statement? Some of the methods used to reduce diesel smoke are as follows
A. Using additives in the fuel
B. Increasing the compression ratio
C. Adherence to proper fuel specification
D. Avoidance of overloading
Answer : B

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

27. 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

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

29. 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

30. The ignition of the charge by some hot surface within the engine before the passage of spark is called
A. Pre-ignition
B. Detonation
C. Ignition delay
D. Auto-ignition
Answer : A

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

32. In a typical medium speed 4-stroke cycle diesel engine
A. Compression starts at 35° after bottom dead center and ends at top dead center
B. Compression starts at bottom dead center and ends at top dead center
C. Compression starts at 10° before bottom dead center and, ends just before top dead center
D. May start and end anywhere
Answer : A

33. In order to mix air and petrol in the required proportion and to supply it to the engine during suction stroke, then _________ is employed.
A. Fuel pump
B. Injector
C. Carburettor
D. None of these
Answer : C

34. Fuel oil consumption guarantees for I .C. engine are usually based on
A. Low heat value of oil
B. High heat value of oil
C. Net calorific value of oil
D. Calorific value of fuel
Answer : B

35. The ratio of the brake power to the indicated power is called
A. Mechanical efficiency
B. Overall efficiency
C. Indicated thermal efficiency
D. Volumetric efficiency
Answer : A

36. The temperature of interior surface of cylinder wall in normal operation is not allowed to exceed
A. 80°C
B. 120°C
C. 180°C
D. 240°C
Answer : C

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

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

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

40. In a typical medium speed, 4-stroke cycle diesel engine
A. Fuel injection starts at 10° before to dead center and ends at 20° after tor dead center
B. Fuel injection starts at top dead center and ends at 20° after top dead center
C. Fuel injection starts at just before top dead center and ends just after top dead center
D. May start and end anywhere
Answer : A

41. The basic requirement of a good combustion chamber is
A. Minimum turbulence
B. Low compression ratio
C. High thermal efficiency and power output
D. Low volumetric efficiency
Answer : C

42. 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

43. 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

44. 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

45. Which of the following statement is correct regarding normal cetane?
A. It is a standard fuel used for knock rating of diesel engines
B. Its chemical name is normal hexadecane
C. It has long carbon chain structure
D. All of the above
Answer : D

46. 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

47. During idling, a petrol engine requires _________ mixture.
A. Lean
B. Rich
C. Chemically correct
D. None of these
Answer : B

48. In a cycle, the spark lasts roughly for
A. 1 sec
B. 0.1 sec
C. 0.01 sec
D. 0.001 sec
Answer : D

49. The pressure inside the cylinder is _________ the atmospheric pressure during the exhaust stroke.
A. Equal to
B. Below
C. Above
D. None of these
Answer : C

50. 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