1000+ Internal Combustion MCQ for NEET PG [Solved]

1. 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

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

3. 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

4. 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

5. 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

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

7. In order to prevent knocking in spark ignition engines, the charge away from the spark plug should have
A. Low density
B. Low temperature
C. Long ignition delay
D. All of these
Answer : D

8. 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

9. 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

10. In a diesel engine, the duration between the time of injection and ignition, is known as
A. Pre-ignition period
B. Delay period
C. Period of ignition
D. Burning period
Answer : B

11. 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

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

13. In a four stroke cycle engine, the sequence of operations is
A. Suction, compression, expansion and exhaust
B. Suction, expansion, compression and exhaust
C. Expansion, compression, suction and exhaust
D. Compression, expansion, suction and exhaust
Answer : A

14. 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

15. 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

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

17. 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

18. A diesel engine as compared to petrol engine (both running and rated load) is
A. More efficient
B. Less efficient
C. Equally efficient
D. Other factors will decide it
Answer : A

19. 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

20. 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

21. The turbine of the turboprop engine is __________ that of the turbojet engine.
A. Same as
B. Smaller than
C. Bigger than
D. None of these
Answer : C

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

23. 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

24. The fuels in order of decreasing knock tendency for spark ignition engines are
A. Paraffin, aromatic, napthene
B. Paraffin, napthene, aromatic
C. Napthene, aromatics, paraffin
D. Napthene, paraffin, aromatic
Answer : B

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

26. 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

27. 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

28. In order to eliminate knocking in compression ignition engines, there should be
A. Short delay period
B. Late auto-ignition
C. Low compression ratio
D. High self ignition temperature of fuel
Answer : A

29. The air-fuel ratio of the petrol engine is controlled by
A. Fuel pump
B. Governor
C. Injector
D. Carburettor
Answer : D

30. 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

31. 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

32. 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

33. 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

34. The colour of exhaust from diesel engine is generally
A. White
B. Bluish
C. Black
D. Violet
Answer : C

35. 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

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

37. A diesel engine is _________ as compared to petrol engine, both running at rated load.
A. Equally efficient
B. Less efficient
C. More efficient
D. None of these
Answer : C

38. 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

39. 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

40. Which of the following is false statement? Excess quantities of sulphur in diesel fuel are Objectionable because it may cause the following
A. Piston ring and cylinder wear
B. Formation of hard coating on piston skirts
C. Oil sludge in the engine crank case
D. Detonation
Answer : D

41. A higher compression ratio causes
A. Pre-ignition
B. Increase in detonation
C. Acceleration in the rate of combustion
D. Any one of these
Answer : D

42. Number of working strokes per min. for a two stroke cycle engine is _________ the speed of the engine in r.p.m.
A. Equal to
B. One-half
C. Twice
D. Four-times
Answer : A

43. The injection pressure in a diesel engine is about
A. 10 bar
B. 100 bar
C. 150 bar
D. 500 bar
Answer : B

44. 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

45. In a coil ignition system of petrol engines, a condenser is connected across the contact breaker in order to
A. Prevent sparking across the gap between the points
B. Cause more rapid break of the primary current, giving a higher voltage in the secondary circuit
C. Both (A) and (B)
D. None of the above
Answer : C

46. 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

47. Air fuel ratio at which a petrol engine cannot work is
A. 8 : 1
B. 10 : 1
C. 15 : 1
D. 20 : 1 and less
Answer : D

48. The specific fuel consumption per BHP hour for diesel engine is approximately
A. 0.15 kg
B. 0.2 kg
C. 0.25 kg
D. 0.3 kg
Answer : B

49. 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

50. The correct sequence of the decreasing order of brake thermal efficiency of the three given basic types of engines is
A. Four stroke C.I. engine, four stroke S.I. engine, two stroke S.I. engine
B. Four stroke S.I. engine, four stroke C.I. engine, two stroke S.I. engine
C. Four stroke C.I. engine, two stroke S.I. engine, four stroke S.I. engine
D. Two stroke S.I. engine, four stroke S.I. engine, four stroke C.I. engine
Answer : A