1000+ Internal Combustion Multiple Choice Question Answer [Solved]

1. In a four stroke cycle diesel engine, the exhaust valve
A. Opens at 30° before bottom dead centre and closes at 10° after top dead centre
B. Opens at 30° after bottom dead centre and closes at 10° before top dead centre
C. Opens at bottom dead centre and closes at top dead centre
D. May open and close anywhere
Answer : A

2. A diesel engine has compression ratio from
A. 6 to 10
B. 10 to 15
C. 15 to 25
D. 25 to 40
Answer : C

3. 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

4. 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

5. 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

6. 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

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

8. 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

9. 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

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

11. 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

12. Thermal efficiency of a two stroke cycle engine is ________ a four stroke cycle engine.
A. Equal to
B. Less than
C. Greater than
D. None of these
Answer : B

13. 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

14. Combustion in compression ignition engines is
A. Homogeneous
B. Heterogeneous
C. Both (A) and (B)
D. Laminar
Answer : B

15. 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

16. 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

17. 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

18. 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

19. Supercharging is the process of
A. Supplying the intake of an engine with air at a density greater than the density of the surrounding atmosphere
B. Providing forced cooling air
C. Injecting excess fuel for raising more loads
D. Supplying compressed air to remove combustion products fully
Answer : A

20. In an internal combustion engine, the process of removing the burnt gases from the combustion chamber of the engine cylinder is known as
A. Scavenging
B. Detonation
C. Supercharging
D. Polymerisation
Answer : A

21. The term scavenging is generally associated with
A. 2-stroke cycle engines
B. 4-stroke cycle engines
C. Aeroplane engines
D. High efficiency engines
Answer : D

22. 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

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

24. For the same compression ratio
A. Otto cycle is more efficient than the Diesel
B. Diesel cycle is more efficient than Otto
C. Both Otto and Diesel cycles are, equally efficient
D. Compression ratio has nothing to do with efficiency
Answer : A

25. In a four stroke cycle diesel engine, the inlet valve
A. Opens at 20° before top dead centre and closes at 40° after bottom dead centre
B. Opens at 20° after top dead centre and closes at 20° before bottom dead centre
C. Opens at top dead centre and closes at bottom dead centre
D. May open and close anywhere
Answer : A

26. A fuel of cetane number 40 has the same ignition quality as a mixture of
A. 40% cetane and 60% alpha methyl naphthalene
B. 40% alpha methyl naphthalene and 60% cetane
C. 40% petrol and 60% diesel
D. 40% diesel and 60% petrol
Answer : A

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. 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. The calorific value of gaseous fuels is expressed in terms of
A. kcal
B. kcal/kg
C. kcal/m²
D. kcal/m³
Answer : D

30. 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

31. Which of the following is not an interns combustion engine?
A. 2-stroke petrol engine
B. 4-stroke petrol engine
C. Diesel engine
D. Steam turbine
Answer : D

32. 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

33. 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

34. The fuel valve in a four stroke cycle diesel engine
A. Opens at 15° after top dead centre and closes at 20° before bottom dead centre
B. Opens at 15° before top dead centre and closes at 20° after top dead centre
C. Opens at top dead centre and closes at bottom dead centre
D. May open and close anywhere
Answer : B

35. The specific fuel consumption per B.P. hour for a petrol engine is about
A. 0.2 kg
B. 0.25 kg
C. 0.3 kg
D. 0.35 kg
Answer : B

36. 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

37. 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

38. The reason for supercharging in any engine is to
A. Increase efficiency
B. Increase power
C. Reduce weight and bulk for a given output
D. Effect fuel economy
Answer : C

39. 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

40. 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

41. The ratio of the volume of charge admitted at N.T.P. to the swept volume of the piston is called
A. Mechanical efficiency
B. Overall efficiency
C. Volumetric efficiency
D. Relative efficiency
Answer : C

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

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

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

45. 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

46. 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

47. 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

48. The cetane (C₁₆H₃₄) which is a straight chain paraffin, is assigned a cetane number of
A. 0
B. 50
C. 100
D. 120
Answer : C

49. Volatility of diesel 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. It catches fire without external aid
D. Indicated by 90% distillation temperature, i.e., when 90% of sample oil has distilled off
Answer : D

50. The operation of forcing additional air under pressure into the engine cylinder is known as
A. Supercharging
B. Carburetion
C. Turbulence
D. Delay period
Answer : A