1000+ Internal Combustion Multiple Choice Question Answer [Solved]

1. 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

2. 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

3. 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

4. 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

5. 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

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

7. In a typical medium speed 4-stroke cycle diesel engine
A. Compression starts at 35° after bottom dead center and ends at top dead center
B. Compression starts at bottom dead center and ends at top dead center
C. Compression starts at 10° before bottom dead center and, ends just before top dead center
D. May start and end anywhere
Answer : A

8. 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

9. In a cycle, the spark lasts roughly for
A. 1 sec
B. 0.1 sec
C. 0.01 sec
D. 0.001 sec
Answer : D

10. The air-fuel ratio of the petrol engine is controlled by
A. Fuel pump
B. Governor
C. Injector
D. Carburettor
Answer : D

11. 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

12. 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

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

14. 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

15. 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

16. 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

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

18. A diesel engine as compared to petrol engine (both running and rated load) is
A. More efficient
B. Less efficient
C. Equally efficient
D. Other factors will decide it
Answer : A

19. In the crankcase method of scavenging, the air pressure is produced by
A. Supercharger
B. Centrifugal pump
C. Natural aspirator
D. Movement of engine piston
Answer : D

20. 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

21. The method of determination of indicated power of a multi cylinder spark ignition engine is by the use of
A. Morse test
B. Prony brake test
C. Motoring test
D. Heat balance test
Answer : A

22. In order to eliminate knocking in compression ignition engines, there should be
A. Short delay period
B. Late auto-ignition
C. Low compression ratio
D. High self ignition temperature of fuel
Answer : A

23. 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

24. 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

25. 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

26. 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

27. Supercharging is the process of supplying the intake air to the engine cylinder at a density _________ the density of the surrounding atmosphere.
A. Equal to
B. Less than
C. Greater than
D. None of these
Answer : C

28. 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

29. 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

30. 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

31. 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

32. In a four stroke cycle engine, the sequence of operations is
A. Suction, compression, expansion and exhaust
B. Suction, expansion, compression and exhaust
C. Expansion, compression, suction and exhaust
D. Compression, expansion, suction and exhaust
Answer : A

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

34. Compression loss in I.C engines occurs due to
A. Leaking piston rings
B. Use of thick head gasket
C. Clogged air inlet slots
D. All of the above
Answer : D

35. 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

36. 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

37. 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

38. Which of the following statement is wrong?
A. In compression ignition engines, detonation occurs near the beginning of combustion.
B. Since the fuel, in compression ignition engines, is injected at the end of compression stroke, therefore, there will be no pre-ignition.
C. To eliminate knock in compression ignition engines, we want to achieve auto-ignition not early and desire a long delay period.
D. In compression ignition engines, because of heterogeneous mixture, the rate of pressure rise is comparatively lower.
Answer : C

39. 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

40. Supercharging is essential in
A. Diesel engines
B. Gas turbines
C. Petrol engines
D. Aircraft engines
Answer : D

41. The thermodynamic cycle on which the petrol engine works, is
A. Otto cycle
B. Joule cycle
C. Rankine cycle
D. Stirling cycle
Answer : A

42. The air standard efficiency of an I.C. engine depends on
A. Fuel used
B. Speed of engine
C. Compression ratio
D. None of these
Answer : C

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

44. 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

45. 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

46. 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

47. 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

48. 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

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

50. It the temperature of intake air in IC engines is lowered, then its efficiency will
A. Increase
B. Decrease
C. Remain same
D. Increase up to certain limit and then decrease
Answer : A