Internal Combustion 1000+ MCQ with answer for LIC ADO

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

2. In a diesel engine, the fuel is ignited by
A. Spark
B. Injected fuel
C. Heat resulting from compressing air that is supplied for combustion
D. Ignition
Answer : C

3. The brake power is the power available
A. In the engine cylinder
B. At the crank shaft
C. At the crank pin
D. None of these
Answer : B

4. 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

5. 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

6. The maximum temperature in the I.C. engine cylinder is of the order of
A. 500-1000°C
B. 1000-1500°C
C. 1500-2000°C
D. 2000-2500°C
Answer : D

7. Fuel consumption of diesel engines is not guaranteed at one quarter load because at such low loads
A. The friction is high
B. The friction is unpredictable
C. The small difference in cooling water temperature or in internal friction has a disproportionate effect
D. The engine is rarely operated
Answer : C

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

9. 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

10. The maximum propulsive efficiency of a turbojet engine is at a speed of
A. 1000 km/h
B. 2000 km/h
C. 2400 km/h
D. 3000 km/h
Answer : C

11. 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

12. 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

13. The scavenging efficiency of a four stroke cycle diesel engine is
A. Below 50%
B. Between 50 and 85%
C. Between 85 and 95%
D. Between 95 and 100%
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 inlet valve of a four stroke cycle internal combustion engine remains open for
A. 130°
B. 180°
C. 230°
D. 270°
Answer : C

16. 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

17. The fuel air ratio in a petrol engine fitted with suction carburettor, operating with dirty air filter as compared to clean filter will be
A. Higher
B. Lower
C. Remain unaffected
D. None of the above
Answer : A

18. Which of the following is the lightest and most volatile liquid fuel?
A. Diesel
B. Kerosene
C. Fuel oil
D. Gasoline
Answer : D

19. In compression ignition engines, swirl denotes a
A. Haphazard motion of the gases in the chamber
B. Rotary motion of the gases in the chamber
C. Radial motion of the gases in the chamber
D. None of the above
Answer : B

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

21. 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

22. 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

23. 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

24. 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

25. 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

26. In loop scavenging, the top of the piston is
A. Flat
B. Contoured
C. Slanted
D. Depressed
Answer : B

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 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

29. 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

30. 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

31. 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

32. 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

33. 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

34. A mixture containing 65% of iso-octane and 35% of normal heptane will have
A. Cetane number 65
B. Octane number 65
C. Cetane number 35
D. Octane number 35
Answer : B

35. In a petrol engine, the fuel supplied to the engine cylinder is mixed with required quantity of air and the mixture is ignited with a
A. Fuel pump
B. Fuel injector
C. Spark plug
D. None of these
Answer : C

36. 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

37. The combustion in compression ignition engines is
A. Homogeneous
B. Heterogeneous
C. Both (A) and (B)
D. None of these
Answer : B

38. In a typical medium speed, 4-stroke cycle diesel engine
A. Fuel injection starts at 10° before to dead center and ends at 20° after tor dead center
B. Fuel injection starts at top dead center and ends at 20° after top dead center
C. Fuel injection starts at just before top dead center and ends just after top dead center
D. May start and end anywhere
Answer : A

39. The delay period in compression ignition engines depends upon
A. Temperature and pressure in the cylinder at the time of injection
B. Nature of the fuel mixture strength
C. Relative velocity between the fuel injection and air turbulence pressure of residual gases
D. All of the above
Answer : D

40. The ignition quality of petrol is expressed by
A. Cetane number
B. Octane number
C. Calorific value
D. All of these
Answer : B

41. 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

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

43. 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

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

45. The _________ engines can work on very lean mixture of fuel.
A. Spark ignition
B. Compression ignition
C. Both (A) and (B)
D. None of these
Answer : B

46. 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

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

48. 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

49. 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

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