Internal Combustion MCQ Solved Paper for SSC GD

1. 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

2. 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

3. 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

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

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

6. 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

7. 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

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. 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

10. 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

11. 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

12. 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

13. 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

14. 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

15. 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

16. The theoretically correct air fuel ratio for petrol engine is of the order of
A. 6 : 1
B. 9 : 1
C. 12 : 1
D. 15 : 1
Answer : D

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

18. The actual volume of fresh charge admitted in 4-stroke petrol engine is
A. Equal to stroke volume
B. Equal to stroke volume and clearance volume
C. Less than stroke volume
D. More than stroke volume
Answer : C

19. The reflectivity depends upon
A. Geometry of the reflector
B. Energy of neutrons
C. Properties of the reflector
D. All of these
Answer : D

20. 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

21. 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

22. 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

23. 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

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 frictional power (F.P.) is given by
A. F.P. = B.P. - I.P.
B. F.P. = I.P. - B.P.
C. F.P. = B.P./I.P.
D. F.P. = I.P./B.P.
Answer : B

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

27. 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

28. 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

29. 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

30. 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

31. In diesel engine the diesel fuel injected into cylinder would burn instantly at about compressed air temperature of
A. 250°C
B. 500°C
C. 1000°C
D. 2000°C
Answer : C

32. The air-fuel ratio in petrol engines is controlled by
A. Controlling valve opening/closing
B. Governing
C. Injection
D. Carburetion
Answer : D

33. The normal heptane (C₇H₁₆) is given a rating of ________ octane number.
A. 0
B. 50
C. 100
D. 120
Answer : A

34. By higher octane number of spark ignition fuel, it is meant that the fuel has
A. Higher heating value
B. Higher flash point
C. Lower volatility
D. Longer ignition delay
Answer : D

35. 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

36. 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

37. 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

38. Scavenging air in diesel engine means
A. Air used for combustion sent under pressure
B. Forced air for cooling cylinder
C. Burnt air containing products of combustion
D. Air used for forcing burnt gases out of engine's cylinder during the exhaust period
Answer : D

39. The power actually developed by the engine cylinder of an I.C. engine is known as
A. Theoretical power
B. Actual power
C. Indicated power
D. None of these
Answer : C

40. 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

41. 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

42. 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

43. 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

44. The object of providing masked inlet valve in the air passage of compression ignition engines is to
A. Enhance flow rate
B. Control air flow
C. Induce primary swirl
D. Induce secondary turbulence
Answer : C

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

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

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

49. 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

50. The increase of cooling water temperature in petrol engine will __________ the knocking tendency.
A. Not effect
B. Decrease
C. Increase
D. None of these
Answer : C