1000+ Internal Combustion Multiple Choice Question Answer [Solved]

1. 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

2. 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

3. The thermal efficiency of diesel engines is about
A. 15 %
B. 30 %
C. 50 %
D. 70 %
Answer : D

4. 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

5. During idling, a petrol engine requires _________ mixture.
A. Lean
B. Rich
C. Chemically correct
D. None of these
Answer : B

6. 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

7. 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

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

10. 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

11. 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

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

13. As compared to air standard cycle, in actual working, the effect of variation in specific heats is to
A. Increase maximum pressure and maximum temperature
B. Reduce maximum pressure and maximum temperature
C. Increase maximum pressure and decrease maximum temperature
D. Decrease maximum pressure and increase maximum temperature
Answer : B

14. 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

15. 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

16. 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

17. 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

18. 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

19. Stoichiometric ratio is
A. Chemically correct air-fuel ratio by weight
B. Chemically correct air-fuel ratio by volume
C. Actual air-fuel ratio for maximum efficiency
D. None of the above
Answer : B

20. 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

21. If V? is the jet velocity and V? is the vehicle velocity, then the propulsive efficiency of a rocket is given by
A. [2(V?/V?)]/ [1 + (V?/V?)²]
B. (V?/V?)/ [1 + (V?/V?)²]
C. V?/(V? + V?)
D. V?/(V? + V?)
Answer : A

22. 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

23. 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

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

25. 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

26. The higher combustion chamber wall temperature in compression ignition engines will _________ knocking tendency.
A. Increase
B. Reduce
C. Not effect
D. None of these
Answer : B

27. The object of providing masked inlet valve in the air passage of compression ignition engines is to
A. Enhance flow rate
B. Control air flow
C. Induce primary swirl
D. Induce secondary turbulence
Answer : C

28. 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

29. 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

30. 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

31. 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

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

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

34. In a four stroke cycle petrol engine, the charge is ignited at
A. 30° before top dead centre
B. 30° after top dead centre
C. 30° before bottom dead centre
D. 30° after bottom dead centre
Answer : A

35. 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

36. 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

37. A diesel engine has
A. One valve
B. Two valves
C. Three valves
D. Four valves
Answer : C

38. 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

39. 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

40. Which of the following does not relate to a spark ignition engine?
A. Ignition coil
B. Spark plug
C. Carburettor
D. Fuel injector
Answer : D

41. 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

42. 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

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

44. The compensating jet in a carburettor supplies almost constant amount of petrol at all speeds because the
A. Jet area is automatically varied depending on the suction
B. The flow from the main jet is diverted to the compensating jet with increase in speed
C. The diameter of the jet is constant and the discharge coefficient is invariant
D. Flow is produced due to the static head in the float chamber
Answer : D

45. Diesel fuel, compared to petrol is
A. Less difficult to ignite
B. Just about the same difficult to ignite
C. More difficult to ignite
D. Highly ignitable
Answer : C

46. 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

47. 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

48. The brake power of a diesel engine, keeping other parameters constant, can be increased by
A. Decreasing the density of intake air
B. Increasing the temperature of intake air
C. Increasing the pressure of intake air
D. Decreasing the pressure of intake air
Answer : C

49. The thermal efficiency of a diesel cycle having fixed compression ratio, with increase in cut-off ratio will
A. Increase
B. Decrease
C. Be independent
D. May increase or decrease depending on other factors
Answer : B

50. A spark plug gap is kept from
A. 0.3 to 0.7 mm
B. 0.2 to 0.8 mm
C. 0.4 to 0.9 mm
D. 0.6 to 1.0 mm
Answer : A