1000+ Internal Combustion MCQ for NMAT [Solved]

1. Which one of the following engines will have heavier flywheel than the remaining ones?
A. 30 kW four-stroke petrol engine running at 1500 r.p.m.
B. 30 kW two-stroke petrol engine running at 1500 r.p.m.
C. 30 kW two-stroke diesel engine running at 750 r.p.m.
D. 30 kW four-stroke diesel engine running at 750 r.p.m.
Answer : A

2. 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

3. 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

4. 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

5. 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

6. 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

7. 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

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

9. The increase of cooling water temperature in petrol engine will __________ the knocking tendency.
A. Not effect
B. Decrease
C. Increase
D. None of these
Answer : C

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

11. The increase of efficiency of a compression ignition engine, as the load decreases, is due to
A. Higher maximum temperature
B. Qualitative governing
C. Quantitative governing
D. Hit and miss governing
Answer : B

12. Which is more viscous lube oil?
A. SEA 30
B. SAE 50
C. SAE 70
D. SAE 80
Answer : D

13. A 75 cc engine has following parameter as 75 cc
A. Fuel tank capacity
B. Lube oil capacity
C. Swept volume
D. Cylinder volume
Answer : C

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

15. The rating of a diesel engine, with increase in air inlet temperature, will
A. Increase linearly
B. Decrease linearly
C. Increase parabolically
D. Decrease parabolically
Answer : B

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

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

18. 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

19. A mixture containing 65% of iso-octane and 35% of normal heptane will have
A. Cetane number 65
B. Octane number 65
C. Cetane number 35
D. Octane number 35
Answer : B

20. 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

21. 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

22. 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

23. 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

24. 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

25. 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

26. 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

27. Morse test is used to determine the I.P. of a
A. Single cylinder petrol engine
B. Four stroke engine
C. Single cylinder diesel engine
D. Multi cylinder engine
Answer : D

28. 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

29. 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

30. 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

31. If the speed of the engine is increased, the indicated power will
A. Increase
B. Decrease
C. Remain same
D. None of these
Answer : A

32. 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

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

34. 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

35. The probability of knocking in diesel engines is increased by
A. High self ignition temperature
B. Low volatility
C. Higher viscosity
D. All of these
Answer : D

36. 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

37. Which of the following statement is wrong?
A. A four stroke cycle engine develops twice the power as that of a two stroke cycle engine
B. For the same power developed, a four stroke cycle engine is lighter, less bulky and occupies less floor area
C. The petrol engines are costly than diesel engines
D. All of the above
Answer : D

38. The purpose of testing an internal combustion engine is
A. To determine the information, which cannot be obtained by calculations
B. To conform the data used in design, the validity of which may be doubtful
C. To satisfy the customer regarding the performance of the engine
D. All of the above
Answer : D

39. 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

40. In petrol engine, using a fixed octane rating fuel and fixed compression ratio, supercharging will _________ the knocking tendency.
A. Not effected
B. Decrease
C. Increase
D. None of these
Answer : C

41. The advancing of spark timing in spark ignition engines will _________ knocking tendency.
A. Increase
B. Reduce
C. Not effect
D. None of these
Answer : A

42. The cam shaft of a four stroke I.C. engine running at 1500 rpm will run at
A. 1500 rpm
B. 750 rpm
C. 3000 rpm
D. Any value independent of engine speed
Answer : B

43. 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

44. 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

45. 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

46. 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

47. 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

48. 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

49. 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

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