Internal Combustion MCQ Solved Paper for IIFT

1. 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

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

3. 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

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

5. 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

6. 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

7. 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

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

9. 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

10. 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

11. A 5 BHP engine running at full load would consume diesel of the order of
A. 0.3 kg/hr
B. 1 kg/hr
C. 3 kg/hr
D. 5 kg/hr
Answer : B

12. 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

13. 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

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

15. The air standard efficiency of an Otto cycle compared to diesel cycle for the given compression ratio is
A. Same
B. Less
C. More
D. More or less depending on power rating
Answer : C

16. 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

17. 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

18. 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

19. The thermal efficiency of a petrol engine is _________ as compared to diesel engine.
A. Same
B. Less
C. More
D. None of these
Answer : B

20. The compression ignition engines are governed by
A. Hit and miss governing
B. Qualitative governing
C. Quantitative governing
D. Combination of (B) and (C)
Answer : B

21. 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

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

23. The exhaust valve in a four stroke cycle petrol engine
A. Opens at 50° before bottom dead centre and closes at 15° after top dead centre
B. Opens at bottom dead centre and closes at top dead centre
C. Opens at 50° after bottom dead centre and closes at 15° before top dead centre
D. May open and close anywhere
Answer : A

24. 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

25. The thermal efficiency of petrol and gas engines is about
A. 15 %
B. 30 %
C. 50 %
D. 70 %
Answer : B

26. In a naturally aspirated diesel engine, the air is supplied by
A. A supercharger
B. A centrifugal blower
C. A vacuum chamber
D. An injection tube
Answer : C

27. 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

28. The working cycle in case of four stroke engine is completed in following number of revolutions of crankshaft
A. 1/2
B. 1
C. 2
D. 4
Answer : C

29. The inlet value of a four stroke cycle I.C engine remains open for nearly
A. 180°
B. 125°
C. 235°
D. 200°
Answer : C

30. If V? is the jet velocity and V? is the vehicle velocity, then propulsive efficiency of a turbojet engine is
A. V?/(V? + V?)
B. V?/(V? + V?)
C. 2V?/(V? + V?)
D. 2V?/(V? + V?)
Answer : C

31. A supercharged engine as compared to an ordinary engine
A. Requires smaller foundation
B. Is lighter
C. Consumes less lubricating oil
D. All of these
Answer : D

32. 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

33. 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

34. 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

35. 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

36. 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

37. 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

38. A heat engine utilises the
A. Calorific value of oil
B. Low heat value of
C. High heat value of oil
D. Mean heat value of oil
Answer : C

39. Alpha-methyl-naphthalene (C?? H??) has a cetane number of
A. 0
B. 50
C. 100
D. 120
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. Antiknock for compression ignition engines is
A. Napthene
B. Tetra ethyl lead
C. Amyl nitrate
D. Hexadecane
Answer : C

42. 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

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

44. 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

45. The working pressure and temperature inside the cylinder of an internal combustion engine is _________ as compared to a steam engine.
A. Low
B. Very low
C. High
D. Very high
Answer : D

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

47. 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

48. 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

49. 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

50. 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