NDA - Internal Combustion 1000+ MCQ [Solved] PDF Download

1. 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

2. The pressure at the end of compression in the case of diesel engine is of the order of
A. 6 kg/cm
B. 12 kg/cm
C. 20 kg/cm
D. 35 kg/cm
Answer : D

3. The thermal efficiency of petrol and gas engines is about
A. 15 %
B. 30 %
C. 50 %
D. 70 %
Answer : B

4. 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

5. The thermal efficiency of diesel engines on weak mixtures is
A. Unaffected
B. Lower
C. Higher
D. Dependent on other factors
Answer : C

6. 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

7. 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

8. 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

9. 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

10. A spark plug gap is kept from
A. 0.3 to 0.7 mm
B. 0.2 to 0.8 mm
C. 0.4 to 0.9 mm
D. 0.6 to 1.0 mm
Answer : A

11. In a four stroke cycle diesel engine, the exhaust valve
A. Opens at 30° before bottom dead centre and closes at 10° after top dead centre
B. Opens at 30° after bottom dead centre and closes at 10° before top dead centre
C. Opens at bottom dead centre and closes at top dead centre
D. May open and close anywhere
Answer : A

12. 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

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

14. As a result of detonation in an I.C. engine, following parameter attains very high value
A. Peak pressure
B. Rate of rise of pressure
C. Rate of rise of temperature
D. Peak temperature
Answer : B

15. Compression ratio of I.C. Engines is
A. The ratio of volumes of air in cylinder before compression stroke and after compression stroke
B. Volume displaced by piston per stroke and clearance volume in cylinder
C. Ratio of pressure after compression and before compression
D. Swept volume/cylinder volume
Answer : A

16. 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

17. 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

18. 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

19. 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

20. 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

21. 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

22. The higher combustion chamber wall temperature in compression ignition engines will _________ knocking tendency.
A. Increase
B. Reduce
C. Not effect
D. None of these
Answer : B

23. 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

24. 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

25. 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

26. The process of breaking up or a liquid into fine droplets by spraying is called
A. Vaporisation
B. Carburetion
C. Ionisation
D. Atomisation
Answer : D

27. The sensing element in the control system of nuclear reactors measures the _________ of the neutron flux in the reactor.
A. Temperature
B. Volume
C. Density
D. None of these
Answer : C

28. In diesel engine, the compression ratio in comparison to expansion ratio is
A. Same
B. Less
C. More
D. Variable
Answer : C

29. 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

30. 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

31. 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

32. The object of supercharging the engine is
A. To reduce mass of the engine per brake power
B. To reduce space occupied by the engine
C. To increase the power output of an engine when greater power is required
D. All of the above
Answer : D

33. The thermal efficiency of a petrol engine is _________ as compared to diesel engine.
A. Same
B. Less
C. More
D. None of these
Answer : B

34. 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

35. 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

36. The brake power of a diesel engine, keeping other parameters constant, can be increased by
A. Decreasing the density of intake air
B. Increasing the temperature of intake air
C. Increasing the pressure of intake air
D. Decreasing the pressure of intake air
Answer : C

37. 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

38. The voltage required to produce a spark across the gap, between the sparking points is
A. 2000 to 4000 volts
B. 4000 to 6000 volts
C. 6000 to 10,000 volts
D. 10,000 to 12,000 volts
Answer : C

39. 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

40. 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

41. 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

42. 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

43. Thermal efficiency of a two stroke cycle engine is ________ a four stroke cycle engine.
A. Equal to
B. Less than
C. Greater than
D. None of these
Answer : B

44. 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

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

46. 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

47. The ratio of the indicated thermal efficiency to the air standard efficiency is known as
A. Mechanical efficiency
B. Overall efficiency
C. Volumetric efficiency
D. Relative efficiency
Answer : D

48. The minimum cranking speed in case of petrol engine is about
A. Half the operating speed
B. One fourth of operating speed
C. 250 - 300 rpm
D. 60 - 80 rpm
Answer : D

49. 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

50. 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