1000+ Internal Combustion MCQ for IBPS PO [Solved]

1. 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

2. 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

3. 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

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

5. 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

6. 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

7. 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

8. The output of a diesel engine can be increased without increasing the engine revolution or size in following way
A. Feeding more fuel
B. Heating incoming air
C. Scavenging
D. Supercharging
Answer : D

9. The thermal efficiency of diesel engines on weak mixtures is
A. Unaffected
B. Lower
C. Higher
D. Dependent on other factors
Answer : C

10. 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

11. 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

12. Diesel engine can work on very lean air fuel ratio of the order of 30: 1. A petrol engine can also work on such a lean ratio provided
A. It is properly designed
B. Best quality fuel is used
C. Cannot work as it is impossible
D. Flywheel size is proper
Answer : C

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

14. The object of supercharging the engine is
A. To reduce mass of the engine per brake power
B. To reduce space occupied by the engine
C. To increase the power output of an engine when greater power is required
D. All of the above
Answer : D

15. 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

16. The operation of forcing additional air under pressure in the engine cylinder is known as
A. Scavenging
B. Turbulence
C. Supercharging
D. Pre-ignition
Answer : C

17. 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

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

19. 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

20. 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

21. In a four stroke cycle petrol engine, the expansion
A. Starts at top dead centre and ends at bottom dead centre
B. Starts at 30° before top dead centre and ends at 50° before bottom dead centre
C. Starts at 30° after top dead centre and ends at 50° after bottom dead centre
D. May start and end anywhere
Answer : B

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

23. The thermal efficiency of a standard Otto cycle for a compression ratio of 5.5 will be
A. 25 %
B. 50 %
C. 70 %
D. 100 %
Answer : B

24. 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

25. 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

26. In case of gas turbines, the gaseous fuel consumption guarantees are based on
A. High heat value
B. Low heat value
C. Net calorific value
D. Calorific value
Answer : B

27. When crude oil is heated, then which of the following hydrocarbon is given off first?
A. Kerosene
B. Gasoline
C. Paraffin
D. Natural gas
Answer : D

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

29. 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

30. 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

31. 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

32. A petrol engine, during suction stroke draws
A. Air only
B. Petrol only
C. A mixture of petrol and air
D. None of these
Answer : C

33. In a four stroke cycle petrol engine, the pressure inside the engine cylinder during the suction stroke is __________ the atmospheric pressure.
A. Equal to
B. Below
C. Above
D. None of these
Answer : B

34. 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

35. 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

36. 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

37. Gaseous fuel guarantees are based on
A. Calorific value of oil
B. Low heat value of oil
C. High heat value of oil
D. Mean heat value of oil
Answer : B

38. Flash point of fuel oil is
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. Temperature at which it catches fire without external aid
D. Indicated by 90% distillation temperature, i.e. when 90% of sample oil has distilled off
Answer : A

39. 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

40. The minimum cranking speed in case of petrol engine is about
A. Half the operating speed
B. One fourth of operating speed
C. 250 - 300 rpm
D. 60 - 80 rpm
Answer : D

41. The two reference fuels used for cetane rating are
A. Cetane and iso-octane
B. Cetane and alpha-methyl naphthalene
C. Cetane and normal heptane
D. Cetane and tetra ethyl lead
Answer : B

42. The pressure at the end of compression, in petrol engines, is approximately
A. 10 bar
B. 20 bar
C. 25 bar
D. 35 bar
Answer : A

43. 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

44. Morse test can be conducted for
A. Petrol engines
B. Diesel engines
C. Multi cylinder engines
D. All of these
Answer : C

45. 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

46. The correct mixture strength (by weight) for petrol is about
A. 14.6 : 1
B. 18.5 : 1
C. 20.4 : 1
D. 22.6 : 1
Answer : A

47. 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

48. 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

49. 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

50. 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