UPSC CSE - Internal Combustion 1000+ MCQ [Solved] PDF Download

1. The injection pressure in a diesel engine is about
A. 10 bar
B. 100 bar
C. 150 bar
D. 500 bar
Answer : B

2. If the temperature of intake air in internal combustion engine increases, then its efficiency will
A. Remain same
B. Decrease
C. Increase
D. None of these
Answer : B

3. 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

4. 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

5. Antiknock for compression ignition engines is
A. Napthene
B. Tetra ethyl lead
C. Amyl nitrate
D. Hexadecane
Answer : C

6. 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

7. 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

8. 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

9. The mean effective pressure obtained from engine indicator indicates the
A. Maximum pressure developed
B. Minimum pressure
C. Instantaneous pressure at any instant
D. Average pressure
Answer : D

10. 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

11. 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

12. The _________ engines can work on very lean mixture of fuel.
A. Spark ignition
B. Compression ignition
C. Both (A) and (B)
D. None of these
Answer : B

13. 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

14. The compensating jet in a carburettor supplies almost constant amount of petrol at all speeds because the
A. Jet area is automatically varied depending on the suction
B. The flow from the main jet is diverted to the compensating jet with increase in speed
C. The diameter of the jet is constant and the discharge coefficient is invariant
D. Flow is produced due to the static head in the float chamber
Answer : D

15. 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

16. 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

17. 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

18. The theoretically correct mixture of air and petrol is
A. 10 : 1
B. 15 : 1
C. 20 : 1
D. 25 : 1
Answer : B

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

20. 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

21. The inlet valve of a four stroke cycle internal combustion engine remains open for
A. 130°
B. 180°
C. 230°
D. 270°
Answer : C

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

23. The knocking in spark ignition engines can be reduced by
A. Retarding the spark
B. Increasing the engine speed
C. Both (A) and (B)
D. None of these
Answer : C

24. For maximum power generation, the air fuel ratio for a petrol engine for vehicles, is of the order of
A. 9 : 1
B. 12 : 1
C. 15 : 1
D. 18 : 1
Answer : B

25. The air standard efficiency of an I.C. engine is given by (where r = Compression ratio, and ? = Ratio of specific heats)
A. 1 - r^{? - 1}
B. 1 + r^{? - 1}
C. 1 - (1/r^{? - 1})
D. None of these
Answer : C

26. 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

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

28. Morse test can be conducted for
A. Petrol engines
B. Diesel engines
C. Multi cylinder engines
D. All of these
Answer : C

29. 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

30. 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

31. 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

32. 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

33. In a four stroke cycle diesel engine, the compression
A. Starts at 40° after bottom dead centre and ends at 10° before top dead centre
B. Starts at 40° before top dead centre and ends at 40° after top dead centre
C. Starts at top dead centre and ends at 40° before bottom dead centre
D. May start and end anywhere
Answer : A

34. 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

35. 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

36. 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

37. The ignition quality of diesel oil is expressed by
A. Cetane number
B. Octane number
C. Calorific value
D. None of these
Answer : A

38. 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

39. 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

40. 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

41. Most high speed compression engines operate on
A. Otto cycle
B. Diesel cycle
C. Dual cycle
D. Carnot cycle
Answer : C

42. 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

43. 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

44. Stoichiometric ratio is
A. Chemically correct air-fuel ratio by weight
B. Chemically correct ar-fuel ratio by volume
C. Actual air-fuel ratio for maximum efficiency
D. None of the above
Answer : B

45. 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

46. The ratio of the work obtained at the crankshaft in a given time to the energy supplied during the same time is called
A. Mechanical efficiency
B. Overall efficiency
C. Indicated thermal efficiency
D. Volumetric efficiency
Answer : B

47. 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

48. 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

49. 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

50. 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