1000+ Internal Combustion Multiple Choice Question Answer [Solved]

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. The octane number of petrol, generally available, is
A. 20 to 40
B. 40 to 60
C. 60 to 80
D. 80 to 100
Answer : D

3. 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

4. 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

5. 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

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

7. As a result of detonation in an I.C. engine, following parameter attains very high value
A. Peak pressure
B. Rate of rise of pressure
C. Rate of rise of temperature
D. Peak temperature
Answer : B

8. Crankcase explosion in I.C. engines usually occurs as
A. First a mild explosion followed by a bi explosion
B. First a big explosion followed by a mil explosion
C. Both mild and big explosions occurs simultaneously
D. Never occurs
Answer : A

9. The loud pulsating noise heard within the cylinder of an internal combustion engine is known as
A. Detonation
B. Turbulence
C. Pre-ignition
D. Supercharging
Answer : A

10. The following volume of air is required for consuming 1 litre of fuel by a four stroke engine
A. 1 m3
B. 5 m3
C. 56 m3
D. 910 m3
Answer : D

11. The voltage required to produce a spark across the gap, between the sparking points is
A. 2000 to 4000 volts
B. 4000 to 6000 volts
C. 6000 to 10,000 volts
D. 10,000 to 12,000 volts
Answer : C

12. 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

13. The air standard efficiency of an I.C. engine depends on
A. Fuel used
B. Speed of engine
C. Compression ratio
D. None of these
Answer : C

14. In petrol engines, advancing of the spark timing will _________ the knocking tendency.
A. Not effect
B. Decrease
C. Increase
D. None of these
Answer : C

15. 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

16. Pre-ignition is caused by the spontaneous combustion of the mixture before the end of the compression stroke, and is due to
A. Cylinder walls being too hot
B. Overheated spark plug points
C. Red hot carbon deposits on cylinder walls
D. Any one of these
Answer : D

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

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

19. 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

20. 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

21. 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

22. 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

23. Which of the following statements is correct?
A. All the irreversible engines have same efficiency
B. All the reversible engines have same efficiency
C. Both Rankine and Carnot cycles have same efficiency between same temperature limits
D. All reversible engines working between same temperature limits have same efficiency
Answer : D

24. 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

25. 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

26. The size of inlet valve of an engine in comparison to exhaust valve is
A. More
B. Less
C. Same
D. More/less depending on capacity of engine
Answer : B

27. 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

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

29. 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

30. In the crankcase method of scavenging, the air pressure is produced by
A. Supercharger
B. Centrifugal pump
C. Natural aspirator
D. Movement of engine piston
Answer : D

31. 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

32. 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

33. Pick up the wrong statement
A. 2-stroke engine can run in any direction
B. In 4-stroke engine, a power stroke is obtained in 4-strokes
C. Thermal efficiency of 4-stroke engine is more due to positive scavenging
D. Petrol engines occupy more space than diesel engines for same power output
Answer : D

34. 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

35. 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

36. 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

37. 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

38. 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

39. The ratio of the work obtained at the crankshaft in a given time to the energy supplied during the same time is called
A. Mechanical efficiency
B. Overall efficiency
C. Indicated thermal efficiency
D. Volumetric efficiency
Answer : B

40. The knocking tendency in compression ignition engines for a given fuel will be
A. Enhanced by decreasing compression ratio
B. Enhanced by increasing compression ratio
C. Dependent on other factors
D. None of the above
Answer : A

41. 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

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

43. The pressure at the end of compression in the case of diesel engine is of the order of
A. 6 kg/cm
B. 12 kg/cm
C. 20 kg/cm
D. 35 kg/cm
Answer : D

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

45. 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

46. Polymerisation is a chemical process in which molecules of a compound become
A. Larger
B. Slowed down
C. Smaller
D. Liquid
Answer : A

47. 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

48. 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

49. 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

50. 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