1000+ Internal Combustion Multiple Choice Question Answer [Solved]

1. Detonation is harmful due to
A. Increase in the rate of heat transfer, there is a reduction in the power output and efficiency of the engine
B. Excessive turbulence which removes most of the insulating gas boundary layer from the cylinder walls
C. High intensity of knock causes crankshaft vibration and the engine runs rough
D. None of the above
Answer : D

2. In a four stroke cycle petrol engine, the compression
A. Starts at 40° after bottom dead centre and ends at 30° before top dead centre
B. Starts at 40° before bottom dead centre and ends at 30° after bottom dead centre
C. Starts at bottom dead centre and ends at top dead centre
D. May start and end anywhere
Answer : A

3. 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

4. Air fuel ratio for idling speed of a petrol engine is approximately
A. 1 : 1
B. 5 : 1
C. 10 : 1
D. 15 : 1
Answer : C

5. 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

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

7. Which one of the following engines will have heavier flywheel than the remaining ones?
A. 30 kW four-stroke petrol engine running at 1500 r.p.m.
B. 30 kW two-stroke petrol engine running at 1500 r.p.m.
C. 30 kW two-stroke diesel engine running at 750 r.p.m.
D. 30 kW four-stroke diesel engine running at 750 r.p.m.
Answer : A

8. 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

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

10. 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

11. 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

12. The expansion of fuel in a four stroke cycle diesel engine
A. Starts at 15° before top dead centre and ends at 30° after top dead centre
B. Starts at top dead centre and ends at 30° after top dead centre
C. Starts at 15° after top dead centre and ends at 30° before bottom dead centre
D. May start and end anywhere
Answer : C

13. 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

14. Diesel as compared to petrol is
A. Highly ignitable
B. More difficult to ignite
C. Less difficult to ignite
D. None of these
Answer : B

15. 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

16. The ratio of the brake power to the indicated power is called
A. Mechanical efficiency
B. Overall efficiency
C. Indicated thermal efficiency
D. Volumetric efficiency
Answer : A

17. Which of the following fuel detonates readily?
A. Benzene
B. Iso-octane
C. Normal heptane
D. Alcohol
Answer : C

18. 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

19. 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

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

21. 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

22. 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

23. 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

24. 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

25. Which of the following statement is correct regarding petrol engines?
A. A fine fuel spray mixed with air is ignited by the heat of compression which is at a high pressure
B. The fuel supplied to the engine cylinder is mixed with necessary amount of air and the mixture in ignited with the help of a spark plug
C. The fuel is first evaporated after passing through a carburettor and is mixed with air before ignition
D. All of the above
Answer : B

26. 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

27. The firing order in an I.C. engine depends upon
A. Arrangement of the cylinders
B. Design of crankshaft
C. Number of cylinders
D. All of these
Answer : D

28. 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

29. 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

30. The ignition of the charge by some hot surface within the engine before the passage of spark is called
A. Pre-ignition
B. Detonation
C. Ignition delay
D. Auto-ignition
Answer : A

31. 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

32. 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

33. 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

34. 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

35. The knocking in diesel engines may be prevented by
A. Reducing the delay period
B. Raising the compression ratio
C. Increasing the inlet pressure of air
D. All of these
Answer : D

36. 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

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

38. Most high speed compression engines operate on
A. Diesel cycle
B. Otto cycle
C. Dual combustion cycle
D. Special type of air cycle
Answer : C

39. If the speed of the engine is increased, the indicated power will
A. Increase
B. Decrease
C. Remain same
D. None of these
Answer : A

40. 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

41. The ratio of indicated thermal efficiency to the corresponding air standard cycle efficiency is called
A. Net efficiency
B. Efficiency ratio
C. Relative efficiency
D. Overall efficiency
Answer : C

42. 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

43. Which of the following is false statement? Excess quantities of sulphur in diesel fuel are Objectionable because it may cause the following
A. Piston ring and cylinder wear
B. Formation of hard coating on piston skirts
C. Oil sludge in the engine crank case
D. Detonation
Answer : D

44. 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

45. An engine indicator is used to determine the following
A. Speed
B. Temperature
C. Volume of cylinder
D. m.e.p. and I.H.P.
Answer : D

46. A 75 cc engine has following parameter as 75 cc
A. Fuel tank capacity
B. Lube oil capacity
C. Swept volume
D. Cylinder volume
Answer : C

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

48. Alpha-methyl-naphthalene (C?? H??) has a cetane number of
A. 0
B. 50
C. 100
D. 120
Answer : A

49. The advancing of spark timing in spark ignition engines will _________ knocking tendency.
A. Increase
B. Reduce
C. Not effect
D. None of these
Answer : A

50. In case of gas turbines, the gaseous fuel consumption guarantees are based on
A. High heat value
B. Low heat value
C. Net calorific value
D. Calorific value
Answer : B