Internal Combustion 1000+ MCQ with answer for NEET

1. 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

2. Most high speed compression engines operate on
A. Otto cycle
B. Diesel cycle
C. Dual cycle
D. Carnot cycle
Answer : C

3. 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

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

5. 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

6. 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

7. 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

8. The power actually developed by the engine cylinder of an I.C. engine is known as
A. Theoretical power
B. Actual power
C. Indicated power
D. None of these
Answer : C

9. 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

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

11. A heat engine utilises the
A. Calorific value of oil
B. Low heat value of
C. High heat value of oil
D. Mean heat value of oil
Answer : C

12. 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

13. 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

14. A diesel engine has
A. 1 valve
B. 2 valves
C. 3 valves
D. 4 valves
Answer : C

15. 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

16. 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

17. 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

18. In a naturally aspirated diesel engine, the air is supplied by
A. A supercharger
B. A centrifugal blower
C. A vacuum chamber
D. An injection tube
Answer : C

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

20. 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

21. The fuel air ratio in a petrol engine fitted with suction carburettor, operating with dirty air filter as compared to clean filter will be
A. Higher
B. Lower
C. Remain unaffected
D. None of the above
Answer : A

22. 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

23. A stoichiometric air-fuel ratio is
A. Chemically correct mixture
B. Lean mixture
C. Rich mixture for idling
D. Rich mixture for over loads
Answer : A

24. 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

25. 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

26. 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

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

28. The knock in diesel engine occurs due to
A. Instantaneous and rapid burning of the first part of the charge
B. Instantaneous auto ignition of last part of charge
C. Delayed burning of the first part of the charge
D. Reduction of delay period
Answer : A

29. 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

30. 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

31. 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

32. 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

33. 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

34. 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

35. The _________ engines can work on very lean mixture of fuel.
A. Spark ignition
B. Compression ignition
C. Both (A) and (B)
D. None of these
Answer : B

36. 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

37. Solid fuel fabricated into various small shapes, which are assembled to form fuel elements, is in the form of
A. Plates
B. Pallets
C. Pins
D. All of these
Answer : D

38. The frictional power (F.P.) is given by
A. F.P. = B.P. - I.P.
B. F.P. = I.P. - B.P.
C. F.P. = B.P./I.P.
D. F.P. = I.P./B.P.
Answer : B

39. 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

40. For the same power developed in I.C. engines, the cheaper system is
A. Naturally aspirated
B. Supercharged
C. Centrifugal pump
D. Turbo charger
Answer : B

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

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

43. The inlet value of a four stroke cycle I.C engine remains open for nearly
A. 180°
B. 125°
C. 235°
D. 200°
Answer : C

44. 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

45. It the temperature of intake air in IC engines is lowered, then its efficiency will
A. Increase
B. Decrease
C. Remain same
D. Increase up to certain limit and then decrease
Answer : A

46. The pressure and temperature at the end of compression stroke in a petrol engine are of the order of
A. 4-6 kg/cm² and 200-250°C
B. 6-12 kg/cm² and 250-350°C
C. 12-20 kg/cm² and 350-450°C
D. 20-30 kg/cm² and 450-500°C
Answer : B

47. 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

48. 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

49. For the same compression ratio
A. Otto cycle is more efficient than the Diesel
B. Diesel cycle is more efficient than Otto
C. Both Otto and Diesel cycles are, equally efficient
D. Compression ratio has nothing to do with efficiency
Answer : A

50. 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