JEE Main - Internal Combustion 1000+ MCQ [Solved] PDF Download

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

2. 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

3. 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

4. The following volume of air is required for consuming 1 litre of fuel by a four stroke engine
A. 1 m3
B. 5 m3
C. 56 m3
D. 910 m3
Answer : D

5. 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

6. 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

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

8. Which of the following is not an interns combustion engine?
A. 2-stroke petrol engine
B. 4-stroke petrol engine
C. Diesel engine
D. Steam turbine
Answer : D

9. 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

10. 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

11. The compression ignition engines are governed by
A. Hit and miss governing
B. Qualitative governing
C. Quantitative governing
D. Combination of (B) and (C)
Answer : B

12. In petrol engines, advancing of the spark timing will _________ the knocking tendency.
A. Not effect
B. Decrease
C. Increase
D. None of these
Answer : C

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

14. A gas engine has a swept volume of 300 cm3 and clearance volume of 25 cm3. Its volumetric efficiency is 0.88 and mechanical efficiency is 0.90. The volume of the mixture taken in per stroke is
A. 248 cm³
B. 252 cm³
C. 264 cm³
D. 286 cm³
Answer : C

15. 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

16. 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

17. 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

18. 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

19. 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

20. Scavenging is usually done to increase
A. Thermal efficiency
B. Speed
C. Power output
D. Fuel consumption
Answer : C

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 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

23. The brake power (B.P.) of the engine is given by (where W = rake 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

24. 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

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

26. Gaseous fuel guarantees are based on
A. Calorific value of oil
B. Low heat value of oil
C. High heat value of oil
D. Mean heat value of oil
Answer : B

27. 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

28. The operation of forcing additional air under pressure in the engine cylinder is known as
A. Scavenging
B. Turbulence
C. Supercharging
D. Pre-ignition
Answer : C

29. 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

30. The cetane (C₁₆H₃₄) which is a straight chain paraffin, is assigned a cetane number of
A. 0
B. 50
C. 100
D. 120
Answer : C

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

32. 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

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

34. The basic requirement of a good combustion chamber is
A. Minimum turbulence
B. Low compression ratio
C. High thermal efficiency and power output
D. Low volumetric efficiency
Answer : C

35. 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

36. Theoretically, a four stroke cycle engine should develop _________ power as that of a two stroke cycle engine.
A. Half
B. Same
C. Double
D. Four times
Answer : A

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

38. As compared to air standard cycle, in actual working, the effect of variation in specific heats is to
A. Increase maximum pressure and maximum temperature
B. Reduce maximum pressure and maximum temperature
C. Increase maximum pressure and decrease maximum temperature
D. Decrease maximum pressure and increase maximum temperature
Answer : B

39. 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

40. The calorific value of gaseous fuels is expressed in terms of
A. kcal
B. kcal/kg
C. kcal/m²
D. kcal/m³
Answer : D

41. 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

42. The air requirement of a petrol engine during starting compared to theoretical air required for complete combustion is
A. More
B. Less
C. Same
D. May be more or less depending on engine capacity
Answer : B

43. The ignition quality of petrol is expressed by
A. Cetane number
B. Octane number
C. Calorific value
D. All of these
Answer : B

44. 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

45. 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

46. The probability of knocking in diesel engines is increased by
A. High self ignition temperature
B. Low volatility
C. Higher viscosity
D. All of these
Answer : D

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

48. Which of the following is false statement? Some of the methods used to reduce diesel smoke are as follows
A. Using additives in the fuel
B. Increasing the compression ratio
C. Adherence to proper fuel specification
D. Avoidance of overloading
Answer : B

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

50. In a four stroke cycle petrol engine, the expansion
A. Starts at top dead centre and ends at bottom dead centre
B. Starts at 30° before top dead centre and ends at 50° before bottom dead centre
C. Starts at 30° after top dead centre and ends at 50° after bottom dead centre
D. May start and end anywhere
Answer : B