1000+ Internal Combustion Multiple Choice Question Answer [Solved]

1. 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

2. An hmh flame speed is obtained in diesel engine when air fuel ratio is
A. Uniform throughout the mixture
B. Chemically correct mixture
C. About 35% of rich mixture
D. About 10% of rich mixture
Answer : D

3. Pick up the false statement
A. Thermal efficiency of diesel engine is about 34%
B. Theoretically correct mixture of air and petrol is approximately 15:1
C. High speed compression engines operate on dual combustion cycle
D. S.I. engines are quality governed engines
Answer : D

4. 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

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

6. 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

7. In a petrol engine, the mixture has the lowest pressure at the
A. Beginning of suction stroke
B. End of suction stroke
C. End of compression stroke
D. None of these
Answer : B

8. 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

9. Air fuel ratio at which a petrol engine cannot work is
A. 8 : 1
B. 10 : 1
C. 15 : 1
D. 20 : 1 and less
Answer : D

10. 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

11. In a diesel engine, the duration between the time of injection and ignition, is known as
A. Pre-ignition period
B. Delay period
C. Period of ignition
D. Burning period
Answer : B

12. 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

13. 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

14. 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

15. 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

16. The theoretically correct mixture of air and petrol is
A. 10 : 1
B. 15 : 1
C. 20 : 1
D. 25 : 1
Answer : B

17. If petrol is used in a diesel engine, then
A. Low power will be produced
B. Efficiency will be low
C. Higher knocking will occur
D. Black smoke will be produced
Answer : C

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

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

20. 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

21. In a four stroke cycle petrol engine, the pressure inside the engine cylinder during the suction stroke is __________ the atmospheric pressure.
A. Equal to
B. Below
C. Above
D. None of these
Answer : B

22. 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

23. 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

24. 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

25. If one cylinder of a diesel engine receives more fuel than the others, then for that cylinder the
A. Exhaust will be smoky
B. Piston rings would stick into piston grooves
C. Engine starts overheating
D. Scavenging occurs
Answer : D

26. 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

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

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

29. 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

30. 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

31. 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

32. 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

33. High speed compression engines operate on
A. Otto cycle
B. Diesel cycle
C. Dual combustion cycle
D. All of these
Answer : C

34. 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

35. 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

36. 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

37. Morse test is used to determine the I.P. of a
A. Single cylinder petrol engine
B. Four stroke engine
C. Single cylinder diesel engine
D. Multi cylinder engine
Answer : D

38. 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

39. Which is more viscous lube oil?
A. SEA 30
B. SAE 50
C. SAE 70
D. SAE 80
Answer : D

40. The brake power (B.P.) of the engine is given by (where W = Brake load or dead load in newtons, l = Length of arm in metres, N = Speed of engine in r.p.m., S = Spring balance reading in newtons, D = Dia. of brake drum in metres, and d = Dia. of rope in metres)
A. B.P = (Wl × 2?N)/60 watts
B. B.P = [(W - S) ?DN]/60 watts
C. B.P = [(W - S) ? (D + d) N]/60 watts
D. All of these
Answer : D

41. 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

42. 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

43. 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

44. 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

45. 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

46. 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

47. 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

48. A diesel engine, during suction stroke, draws
A. Air only
B. Diesel only
C. A mixture of diesel and air
D. None of these
Answer : A

49. 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

50. The increase of efficiency of a compression ignition engine, as the load decreases, is due to
A. Higher maximum temperature
B. Qualitative governing
C. Quantitative governing
D. Hit and miss governing
Answer : B