Unit-II : Fundamental of Mechanical Engineering MCQ
1. 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
2. In an internal combustion engine, the process of removing the burnt gases from the combustion chamber of the engine cylinder is known as
(A) Scavenging
(B) Detonation
(C) Supercharging
(D) Polymerisation
Answer: a
3. 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
4. Which of the following is the lightest and most volatile liquid fuel?
(A) Diesel
(B) Kerosene
(C) Fuel oil
(D) Gasoline
Answer: d
5. 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
6. The rating of a diesel engine, with increase in air inlet temperature, will
(A) Increase linearly
(B) Decrease linearly
(C) Increase parabolically
(D) Decrease parabolically
Answer: b
7. Pick up the wrong statement about
supercharging
(A) Supercharging reduces knocking in diesel engines
(B) There can be limited supercharging in petrol engines because of detonation
(C) Supercharging at high altitudes is essential
(D) Supercharging results in fuel economy
Answer: d
8. 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
9. 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
10. The ignition quality of petrol is expressed by
(A) Cetane number
(B) Octane number
(C) Calorific value
(D) All of these
Answer: b
11. 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
12. 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
13. 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
14. 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
15. Which of the following medium is compressed in a Diesel engine cylinder?
(A) Air alone
(B) Air and fuel
(C) Air and lub oil
(D) Fuel alone
Answer: a
16. 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: a
17. 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
18. 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
19. 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
20. 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
21. In a naturally aspirated diesel engine, the air is supplied by
(A) A supercharger
(B) A centrifugal blower
(C) A vacuum chamber
(D) An injection tube
Answer: c
22. Which of the following is not an intern’s combustion engine?
(A) 2-stroke petrol engine
(B) 4-stroke petrol engine
(C) Diesel engine
(D) Steam turbine
Answer: d
23. The spark ignition engines are governed by
(A) Hit and miss governing
(B) Qualitative governing
(C) Quantitative governing
(D) Combination of (B) and (C)
Answer: c
24. 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
25. 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
26. Scavenging is usually done to increase
(A) Thermal efficiency
(B) Speed
(C) Power output
(D) Fuel consumption
Answer: c
27. 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
28. 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
29. ____ is a chemical reaction in which certain elements of the fuel like hydrogen and carbon combine with oxygen liberating heat energy and causing an increase in temperature of the gases.
(A) Compression
(B)Expansion
(C) Combustion
(D) None of the mentioned
Answer: c
30. In spark ignition engines a nearly ____ mixture of air and fuel is formed in the carburettor.
(A) heterogeneous
(B)homogeneous
(C) solid
(D) none of the mentioned
Answer: b
31. The thermal efficiency of a standard Otto cycle for a compression ratio of 5.5 will be _____
(A) 25%
(B) 50%
(C) 70%
(D) 100%
Answer: b
32. The efficiency of an Otto cycle is increased by increasing _____
(A) pressure ratio
(B) compression ratio
(C) temperature ratio
(D) none of the mentioned
Answer: b
33. The Otto cycle consists of _____
(A) two constant pressure processes and two constant volume processes
(B)two constant pressure and two constant entropy processes
(C) two constant volume processes and two constant entropy processes
(D) none of the mentioned
Answer: b
34. The thermal efficiency of theoretical Otto cycle _____
(A) decreases with increase in compression ratio
(B) increases with decrease in compression ratio
(C) does not depends upon the pressure ratio
(D) none of the mentioned
Answer: c
35. What is the work output of the theoretical Otto cycle?
(A) increases with increase in compression ratio
(B) increases with increase in pressure ratio
(C) increases with increase in compression & pressure ratio
(D) none of the mentioned
Answer: c
36. The mean effective pressure of an Otto Cycle increases with an increase in _____
(A) pressure ratio
(B) compression ratio
(C) temperature ratio
(D) none of the mentioned
Answer: b
37. In Otto cycle, heat addition takes place at _____
(A) constant temperature
(B) constant pressure
(C) constant volume
(D) none of the mentioned
Answer: c
38. If compression ratio of an engine working on Otto cycle is increased from 5 to 6, its air standard efficiency will increase by_____
(A) 1%
(B) 20%
(C) 16.67%
(D) 8%
Answer: d
39. If the compression ratio of an engine working on Otto cycle is increased from 5 to 7, thepercentage increase in efficiency will be
_____
(A) 2%
(B) 4%
(C) 8%
(D) 14%
Answer: d
40. The constant volume cycle is also called_____
(A) Carnot cycle
(B) Joule cycle
(C) Diesel cycle
(D) Otto cycle
Answer: d
41. What does 1 Tonne (TR) in refrigeration mean?
(A) Weight of gases
(B) Weight of coolant
(C) Capacity of 1 tonne air to be cooled to 0 C in 24 hours
(D) Capacity of 1 tonne water to be cooled to 0 C in 24 hours
Answer: d
42. 1 Tonne = __ KJ/s.
(A) 2.67
(B) 1.087
(C) 3.5
(D) 232.6
Answer: c
43. Which is the S.I. unit to measure pressure in refrigeration?
(A) Newton
(B)Joule
(C) Pascal
(D)Bar
Answer: c
44. 0 Kelvin = __ Celsius.
(A)-273 C
(B) 273 C
(C) -273 K
(D) 0 C
Answer: a
45. The heat removing capacity of one tonne refrigeration is equal to?
(A) 210 KJ/min
(B) 620 KJ/min
(C) 240 KJ/min
(D) 430 KJ/min
Answer: a
46. What does 35 Celsius (C) mean on Kelvin scale (K)?
(A) 350
(B) 135
(C) 308
(D) 298
Answer: c
47. What is S.I. unit of refrigeration?
(A) J/min
(B) KJ/s
(C) KWh
(D) Kg/s
Answer: b
48. 1 N/mm2 = ___ mm of Hg (mercury).
(A) 1
(B) 256
(C) 760
(D) 720
Answer: c
49. What is the S.I. unit required to measure the work done in refrigeration is?
(A) Joule/kg
(B) KJ/kg
(C) Joule/m. s
(D) Joule/s
Answer: d
50. Which one of the following is not a component of a simple air cooling system?
(A) Main compressor
(B) Cooling fan
(C) Heat exchanger
(D) Generator
Answer: d
51. Which of the following is true about the optimum effective temperature for human comfort?
(A) Same in winter and summer
(B) Not dependent on season
(C) Lower in winter than in summer
(D) Higher in winter than in summer
Answer: c
52. The heat production from a normal healthy man when asleep is about ___
(A) 50 W
(B) 40 W
(C) 70 W
(D) 60 W
Answer: d
53. When the heat stored in the body is____ the human body feels comfortable.
(A) zero
(B) infinite
(C) positive
(D) negative
Answer: a
54. Which of the following does not mainly a factor of dependency for the degree of warmth or cold?
(A) Relative humidity
(B) WBT
(C) Air velocity
(D) DBT
Answer: d
55. What is the term (C)O.P. referred in terms of refrigeration?
(A) Capacity of Performance
(B) Co-efficient of Plant
(C) Co-efficient of Performance
(D) Cooling for Performance
Answer: c
56. (C)O.P. can be expressed by which equation?
(A) WorkDoneRefrigerationeffece
(B) RefrigerationeffectWorkDone
(C) WorkDoneHeatTransfer
(D) HeatTransferWorkDone
Answer: b
57. What is the term relative (C)O.P. referred in terms of refrigeration?
(A) Actual(C)O.P.Theoretical(C)O.P.
(B) Theoretical(C)O.P.Actual(C)O.P.
(C) Actual(C)O.P.Average(C)O.P.
(D) Average(C)O.P.Theoretical(C)O.P.
Answer: a
58. Find the (C)O.P. of a refrigeration system if the work input is 40 KJ/kg and refrigeration effect produced is 130 KJ/kg of refrigerant
flowing.
(A) 3.00
(B) 2.25
(C) 3.75
(D) 3.25
Answer: d
59. Find the Relative (C)O.P. of a refrigeration system if the work input is 60 KJ/kg and refrigeration effect produced is 130 KJ/kg refrigerant flowing. Also Theoretical (C)O.P. is
(A) 0.65
(B) 0.79
(C) 0.72
(D) 0.89
Answer: c
60. Find the (C)O.P. of a refrigeration system if the work input is 30 KJ/kg and refrigeration effect produced is 120 KJ/kg of refrigerant flowing.
(A) 3.00
(B) 4.00
(C) 0.75
(D) 0.25
Answer: b
61. Which equation represents efficiency in general?
(A) WorkDoneRefrigerationeffect
(B) HeatTrasferWorkDone
(C) WorkDoneHeatTransfer
(D) RefrigerationeffectWorkDone
Answer: c
62. The Co-efficient of Performance is always ____
(A) greater than 1
(B) less than 1
(C) equal to 1
(D) zero
Answer: a
63. In a refrigerating machine, if the lower temperature is fixed, then the (C)O.P. of machine can be increased by?
(A) Increasing the higher temperature
(B) Decreasing the higher temperature
(C) Operating the machine at lower speed
(D) Operating the machine at higher speed
Answer: b
64. If a condenser and evaporator temperatures are 120 K and 60 K respectively, then reverse Carnot (C)O.P is ___
(A) 0.5
(B) 1
(C) 3
(D) 2
Answer: b
65. The (C)O.P. of reverse Carnot cycle is most strongly dependent on which of the following?
(A) Evaporator temperature
(B) Condenser temperature
(C) Specific heat
(D) Refrigerant
Answer: a
66. If a condenser and evaporator temperatures are 312 K and 273 K respectively, then reverse Carnot (C)O.P is ___
(A) 5
(B) 6
(C) 7
(D) 8
Answer: c
67. The (C)O.P for reverse Carnot refrigerator is 2. The ratio of lowest temperature to highest temperature will be ___
(A) twice
(B) half
(C) four times
(D) three times
Answer: d
68. If a condenser and evaporator temperatures are 250 K and 100 K respectively, then reverse Carnot (C)O.P is ___
(A) 5.5
(B) 1.5
(C) 2.5
(D) 3.0
Answer: c
69. The reverse Carnot cycle (C)O.P. can be expressed as ___ (Where t1 is the lower temperature and t2 is the higher temperature).
(A) (t1−t2)/t2
(B) (t2−t1)/t2
(C) (t2−t1)/(t1−t2)
(D) (t2−t1)/t1
Answer: d
70. What is the difference between Heat Pump and Refrigerator?
(A) Heat Pump Gives efficiency and refrigerator gives (C)O.P.
(B) Both are similar
(C) Both are almost similar, just the desired effect is different
(D) Work is output in refrigerator and work is input in heat pump
Answer: c
71. What is the equation between efficiency of Heat engine and (C)O.P. of heat pump?
(A) ηE = ((C)O.P.)P
(B) ηE = 1 / ((C)O.P.)P
(C) ηE / ((C)O.P.)P = 1
(D) ηE x ((C)O.P.)P = 0
Answer: b
72. How is the Relative coefficient of performance represented?
(A) Theoretical (C)O.P. / Actual (C)O.P.
(B) Actual (C)O.P. / Theoretical (C)O.P.
(C) Theoretical (C)O.P. x Actual (C)O.P.
(D) 1 / Theoretical (C)O.P. x Actual (C)O.P.
Answer: b
73. (C)O.P. of the heat pump is always ___
(A) one
(B) less than One
(C) greater than One
(D) zero
Answer: c
74. For the systems working on reversed Carnot cycle, what is the relation between (C)O.P. of Refrigerator i.e. ((C)O.P.)R and Heat Pump i.e.
((C)O.P)P?
(A) ((C)O.P.)R + ((C)O.P)P = 1
(B) ((C)O.P.)R = ((C)O.P)P
(C) ((C)O.P.)R = ((C)O.P)P – 1
(D) ((C)O.P.)R + ((C)O.P)P + 1 = 0
Answer: c
75. If the reversed Carnot cycle operating as a heat pump between temperature limits of 364 K and 294 K, then what is the value of (C)O.P?
(A) 4.2
(B) 0.19
(C) 5.2
(D) 0.23
Answer: c
76. A reversed Carnot cycle is operating between temperature limits of (-) 33°C and (+) 27°(C) If it acts as a heat engine gives an efficiency of 20%. What is the value of (C)O.P. of a heat pump operating under the same conditions?
(A) 6.5
(B) 8
(C) 5
(D) 2.5
Answer: c
77. If the coefficient of performance of the refrigerator is 4.67, then what is the value of the coefficient of performance of the heat pump operating under the same conditions?
(A) 3.67
(B) 5.67
(C) 0.214
(D) 9.34
Answer: b
78. A heat pump is used to maintain a hall at 30°C when the atmospheric temperature is 15°(C) The heat loss from the hall is 1200 kJ/min. Calculate the power required to run the heat pump if its (C)O.P. is 40% of the Carnot machine working between the same temperatur limits.
(A) 0.495
(B) 4.04
(C) 0.247
(D) 8.08
Answer: c
79. A heat pump which runs (1/3)rd of time removes on an average 2400 kJ/hr of heat. If power consumed is 0.25 kW, what is the value of the (C)O.P.?
(A) 4
(B) 2
(C) 8
(D) 6
Answer: c
80. (C)O.P. of the refrigerator is always ____ the (C)O.P. of the heat pump when both are working between the same temperature limits.
(A) less than
(B) greater than
(C) equal to
(D) inverse of
Answer: a
