McqMate
These multiple-choice questions (MCQs) are designed to enhance your knowledge and understanding in the following areas: Mechanical Engineering .
| 51. |
What is the function of safety valves in the boiler? |
| A. | to prevent excessive steam pressure |
| B. | to prevent excessive air pressure |
| C. | to prevent water pressure |
| D. | to prevent from rising temperatures |
| Answer» A. to prevent excessive steam pressure | |
| Explanation: the function of safety valve is to prevent the excessive steam pressure inside the boiler drum exceeding the design | |
| 52. |
How many types of safety valves are used in boiler in practice? |
| A. | 1 |
| B. | 2 |
| C. | 3 |
| D. | 4 |
| Answer» B. 2 | |
| Explanation: two types of safety valves are used in practice | |
| 53. |
What happens due to high temperature of feeds water in the economizer? |
| A. | fuel consumption increases |
| B. | fuel mechanical efficiency increases |
| C. | fuel consumption decreases |
| D. | fuel mechanical efficiency decreases |
| Answer» C. fuel consumption decreases | |
| Explanation: function of the economizer is to recover a portion of heat of the exhaust gases before the flue gases enter the chimney and discharged to the atmosphere. due to the high temperature of feed water, fuel consumption reduces. this increases the overall efficiency of the boiler. | |
| 54. |
What is the function of superheater in the boiler? |
| A. | increase the temperature of steam |
| B. | reheat the steam |
| C. | superheat the feed water |
| D. | to heat the fuel gas |
| Answer» A. increase the temperature of steam | |
| Explanation: function of the superheater is to increase the temperature of steam above its saturation temperature. as heat contained in unit mass of superheated steam is more than dry saturated or wet steam, it is extensively used in steam power plants. | |
| 55. |
What is the function Air heater in the boiler? |
| A. | preheat the air before entering the boiler |
| B. | recover the heat from flue gas |
| C. | heating of economizer tubes |
| D. | reheat the gas coming out of economizer |
| Answer» B. recover the heat from flue gas | |
| Explanation: function of air preheater is to recover the heat of a portion of exhaust flue gases before the flue gases enter the chimney. it is places along the passage of the exhaust flue gases in between the economizer and the chimney. | |
| 56. |
What is the function of the feed water pump of a boiler? |
| A. | pump water at high pressure |
| B. | to pump water at lower pressure |
| C. | to pull back the water from boiler |
| D. | to convert steam into water after the boiler process |
| Answer» A. pump water at high pressure | |
| Explanation: function of feed water pump is to pump water at high pressure to the water space of the boiler drum. there are many types of feed pumps, in which they are | |
| 57. |
Rotary pumps are driven by |
| A. | electric motors |
| B. | batteries |
| C. | diesel engines |
| D. | biogas fuel |
| Answer» A. electric motors | |
| Explanation: rotary pumps are driven by electric motors. water is pumped due to rotary action of the impeller. rotary pumps are invented by charles c barnes. it is a positive displacement pump. the efficiency of these pumps depends on the percentage of slip to the total quantity displaced. | |
| 58. |
Which fuel is prepared by heating bituminous coal continuously for 15 to 18 hours in closed chamber? |
| A. | charcoal |
| B. | anthracite |
| C. | coke |
| D. | briquette coal |
| Answer» C. coke | |
| Explanation: coal is prepared by heating bituminous coal continuously for 15 to 18 hours in closed chamber in the absence of air 500oc to 700oc. during this process the volatile matter is removed from the coal, leaving a dull black color to coke. it is a hard porous structure and smokeless. it contains 85 to 95% carbon. when the bituminous coal is heated between 900oc to 1000oc, hard coke | |
| 59. |
Which fuel is produced by powdering low grade coal with high ash content? |
| A. | coke |
| B. | pulverized coal |
| C. | charcoal |
| D. | briquette coal |
| Answer» B. pulverized coal | |
| Explanation: pulverized coal is prepared by powdering low grade coal with high ash content. dry coal is pulverized in pulverizing mills. it burns most efficiently when mixed with air and hence it is used in most of the power plants. | |
| 60. |
Which is the correct advantage of solid fuels out of the given option? |
| A. | they have low ignition temperature |
| B. | they produce small amount of smoke |
| C. | they have higher calorific value |
| D. | they do not form any clinker |
| Answer» A. they have low ignition temperature | |
| Explanation: they have low ignition temperature’. ignition temperature is the minimum temperature at which a substance starts to burn. different fuels have different ignition temperature. some fuels have low ignition temperature and some have high ignition temperature. the fuels that have low ignition temperature are highly inflammable and burn quickly at the spark of fire. while some fuels that have high ignition | |
| 61. |
Choose the proper disadvantage of solid fuels out of the given option? |
| A. | they produce lot of smoke |
| B. | they have low ignition temperature |
| C. | they are high in production cost |
| D. | they cannot be easily transported |
| Answer» A. they produce lot of smoke | |
| Explanation: solid fuels tend to produce lot of smoke because they have large percentage of ash content. they are also brittle in nature and they contain some amount of ash in it when they are in ground. due to their brittleness, it is common nature of solid fuels that they break into pieces while mining and transporting and form ash. | |
| 62. |
In what forms are liquid fuels available in nature? |
| A. | light distillate |
| B. | petroleum spirit |
| C. | petroleum naphtha |
| D. | crude petroleum |
| Answer» D. crude petroleum | |
| Explanation: liquid fuels are available in nature in the form of crude petroleum. all commercial liquid fuels are derived from crude petroleum or crude oil. the crude oil, as it comes out from oil wells contains 83- 87% carbon, 10-14% hydrogen and small percentages of sulfur, nitrogen, oxygen and gases containing mainly ethane and methane. | |
| 63. |
Name the process used to eliminate impurities present in crude oil? |
| A. | distillation |
| B. | filtration |
| C. | sedimentation |
| D. | coagulation |
| Answer» A. distillation | |
| Explanation: the impurities present in the crude oil are eliminated by the process of refining oil by distillation. it is based on the principle that boiling points of various hydrocarbons increase with an increase in molecular weight and when distilled, the crude oil is separated into gasoline, kerosene, fuel oil or reduced crude oil. | |
| 64. |
Which fuel is heavier than petrol but less volatile and it is commonly used as domestic fuel? |
| A. | diesel |
| B. | distilled fuel |
| C. | kerosene |
| D. | alcohol |
| Answer» C. kerosene | |
| Explanation: kerosene is heavier than gasoline but less volatile than it. it has a specific gravity ranging from 0.78 to 0.85. it is obtained between 150 to 300oc. it is mainly used in aviation gas turbines as jet | |
| 65. |
Which fuel is slightly heavier than kerosene and is produced in petroleum fractions? |
| A. | diesel |
| B. | crude oil |
| C. | gasoline |
| D. | distillate |
| Answer» D. distillate | |
| Explanation: distillate is slightly heavier than kerosene and is used as fuel and | |
| 66. |
Which fuel has higher thermodynamic efficiency in liquid fuels? |
| A. | diesel |
| B. | petrol |
| C. | kerosene |
| D. | lpg |
| Answer» A. diesel | |
| Explanation: diesel is heavier than kerosene. it has specific gravity ranging from 0.86 to | |
| 67. |
Which liquid fuel has a wider composition than diesel and used in furnaces of oil fired boiler? |
| A. | fuel oil |
| B. | petrol |
| C. | distillate |
| D. | alcohol |
| Answer» A. fuel oil | |
| Explanation: fuel oil is similar to diesel but has wider composition than diesel. it is used in furnaces of oil fired boilers. broadly speaking, fuel oil is any liquid fuel that is burned in furnace or boiler for the generation of power, except oil is having a flash point of approximately 42oc and oils burned in cotton or wool-wick burners. | |
| 68. |
Which is the artificial liquid fuel obtained by fermentation process? |
| A. | fuel oil |
| B. | alcohol |
| C. | distillate |
| D. | kerosene |
| Answer» B. alcohol | |
| Explanation: alcohol is an artificial fuel obtained from vegetable matter by fermentation process. it is used in many chemical processes. the first four aliphatic alcohols (methanol, propanol, ethanol and butanol) are of interest as fuels because they can be synthesized chemically or biologically. the general chemical formula for alcohol fuel is cnh2n+1oh. | |
| 69. |
Which among the following fuels need excess amount of air for complete combustion? |
| A. | natural fuels |
| B. | liquid fuels |
| C. | gaseous fuels |
| D. | artificial solid fuels |
| Answer» D. artificial solid fuels | |
| Explanation: artificial solid fuels need excess amount of air for complete combustion because they have low calorific value compared to liquid fuels and the rate of combustion of solid fuels cannot be easily controlled. they have tendency to form clinkers at high temperatures. | |
| 70. |
Which of the following is not a type of steam turbine? |
| A. | impulse turbine |
| B. | reaction turbine |
| C. | pelton wheel turbine |
| D. | axial flow type turbine |
| Answer» C. pelton wheel turbine | |
| Explanation: pelton wheel turbine is a water | |
| 71. |
Majority of the turbines are axial flow type. |
| A. | true |
| B. | false |
| Answer» A. true | |
| Explanation: in axial flow type turbines the steam flows over the blades in a direction parallel to the axis of the wheel. in radial flow turbines the blades are arranged radially so that the steam enters at the blade tip nearest the axis of the wheel and flows towards the circumference. | |
| 72. |
Which turbines are employed for driving alternator at synchronous speed? |
| A. | central station turbine |
| B. | reheating turbine |
| C. | extraction turbine |
| D. | extraction induction turbine |
| Answer» A. central station turbine | |
| Explanation: central turbines are for driving the alternator at synchronous speed. in reheating turbine steam is returned back to the boiler after partial expansion for superheating and then allowed to expand to back pressure. in extraction turbines steam leaves the turbine casing before the exhaust, for feed water heating. | |
| 73. |
Non Condensing steam turbine can also be called as |
| A. | extraction steam turbine |
| B. | back pressure steam turbine |
| C. | impulse steam turbine |
| D. | none of the mentioned |
| Answer» B. back pressure steam turbine | |
| Explanation: the other name for non condensing turbines is back pressure turbines. | |
| 74. |
Steam turbine is classified on basis of |
| A. | type of blades |
| B. | exhausting condition |
| C. | type of steam flow |
| D. | all of the mentioned |
| Answer» D. all of the mentioned | |
| Explanation: steam turbines are classified by type of blades, exhausting condition, type of steam flow, division of steam flow, type of compounding. | |
| 75. |
High pressure turbine is a Non-Condensing turbine due to |
| A. | exhaust conditions |
| B. | axial flow of the steam |
| C. | pressure-velocity compounding |
| D. | velocity compounding |
| Answer» A. exhaust conditions | |
| Explanation: for high pressure turbines exhaust conditions are controlled by regulating valve which makes them to come under the category of non-condensing turbines. | |
| 76. |
Impulse blades are in the shape of |
| A. | rain drop |
| B. | circular |
| C. | half moon |
| D. | none of the mentioned |
| Answer» C. half moon | |
| Explanation: blades used in impulse turbines are half moon shaped because as steam enters the moving blade it pushes the blade forward. | |
| 77. |
Astern turbines are used in |
| A. | power generation |
| B. | marine purposes |
| C. | aircraft |
| D. | none of the mentioned |
| Answer» B. marine purposes | |
| Explanation: astern turbines are those classified based on exhaust conditions and are used for marine purposes. | |
| 78. |
Cross compound steam turbines are once used in |
| A. | generation of electricity |
| B. | marine ships |
| C. | automobiles |
| D. | none of the mentioned |
| Answer» B. marine ships | |
| Explanation: cross compound turbines are once used in marine ships before two stroke diesel engines. | |
| 79. |
When steam reaches turbine blades the type of force responsible for moving turbine blades are |
| A. | axial force |
| B. | shear force |
| C. | longitudinal force |
| D. | none of the mentioned |
| Answer» A. axial force | |
| Explanation: axial force pushes the turbine blade forward and causes movement in turbine blade. | |
| 80. |
Multi stage arrangement of turbines is called as |
| A. | impulse turbine |
| B. | reaction turbine |
| C. | compounding |
| D. | none of the mentioned |
| Answer» C. compounding | |
| Explanation: multi stage arrangement of turbines reduces the pressure loss and velocity losses and hence it is called as compounding. | |
| 81. |
Compounding efficiency at low speed. |
| A. | decrease |
| B. | increase |
| C. | maximizes |
| D. | none of the mentioned |
| Answer» B. increase | |
| Explanation: even at low speeds velocity wastage is prevented and hence efficiency is increased. | |
| 82. |
In velocity compounded turbines flow passage is from |
| A. | moving blades to fixed nozzles |
| B. | fixed nozzles to moving blades |
| C. | fixed blades to moving nozzles |
| D. | none of the mentioned |
| Answer» D. none of the mentioned | |
| Explanation: in velocity compounded turbines velocity drop is maintained in stages and hence reducing velocity loses. hence in velocity compounded turbines flow passage is from fixed nozzles to multiple rows of | |
| 83. |
A velocity compounded impulse turbine is also called as |
| A. | curtis wheel |
| B. | pressure compounded |
| C. | curtis wheel & pressure compounded |
| D. | none of the mentioned |
| Answer» A. curtis wheel | |
| Explanation: velocity compounded turbines are invented by a scientist called curtis and hence it is named after his name. | |
| 84. |
Reaction turbine is also called as |
| A. | impulse turbine |
| B. | curtis wheel |
| C. | parsons turbine |
| D. | none of the mentioned |
| Answer» C. parsons turbine | |
| Explanation: reaction turbine was invented by a scientist names parson and hence it was named after his name. | |
| 85. |
A turbine comprising of fixed blades and moving nozzles is called as reaction turbines. |
| A. | true |
| B. | false |
| Answer» A. true | |
| Explanation: in reaction turbines the reaction produced when steam hits the turbine is also utilized to produce power output. | |
| 86. |
Which of these is not an application of back pressure turbine? |
| A. | desalination of sea water |
| B. | filtration of water |
| C. | process industries |
| D. | petrochemical installations |
| Answer» B. filtration of water | |
| Explanation: the applications of back pressure turbine are desalination of sea water, process industries, petrochemical installations, district heating and also for driving compressors and feed pumps. | |
| 87. |
Pass-out turbines are used in which of these cases? |
| A. | relatively high back pressure |
| B. | small heating requirement |
| C. | only relatively low back pressure |
| D. | both relatively high back pressure and small heating requirement |
| Answer» D. both relatively high back pressure and small heating requirement | |
| Explanation: pass-out turbines are used in cases of relatively high back pressure and small heating requirements. they are used in cases where a certain quantity of steam is continuously extracted from the turbine at an intermediate stage for heating purposes at the desired temperature and pressure. | |
| 88. |
Heat exchangers are classified into how many categories? |
| A. | 1 |
| B. | 2 |
| C. | 3 |
| D. | 4 |
| Answer» D. 4 | |
| Explanation: nature of heat exchange process, relative direction of motion of fluid, mechanical design of heat exchange surface and physical state of heat exchanging fluids. | |
| 89. |
Based upon the nature of heat exchange process, the heat exchangers are classified into how many categories |
| A. | 1 |
| B. | 2 |
| C. | 3 |
| D. | 4 |
| Answer» C. 3 | |
| Explanation: direct contact, regenerators and recuperators. | |
| 90. |
Which type of flow arrangement is this? |
| A. | counter flow |
| B. | parallel flow |
| C. | regenerator |
| D. | shell and tube |
| Answer» B. parallel flow | |
| Explanation: in this type of arrangement, the fluids enter the unit from the same side, flow in the same direction and leave from the same side. | |
| 91. |
Which of the following is not an example of recuperators type heat exchanger? |
| A. | automobile radiators |
| B. | condensers |
| C. | chemical factories |
| D. | oil heaters for an aero plane |
| Answer» C. chemical factories | |
| Explanation: recuperators are not used in chemical factories. | |
| 92. |
In how many categories heat exchangers are classified on the basis of direction of flow of fluids? |
| A. | 4 categories |
| B. | 3 categories |
| C. | 2 categories |
| D. | 1 categories |
| Answer» B. 3 categories | |
| Explanation: parallel, counter and cross flow. | |
| 93. |
In how many categories heat exchangers are classified on the basis of physical state of heat exchanging fluids? |
| A. | 1 |
| B. | 2 |
| C. | 3 |
| D. | 4 |
| Answer» B. 2 | |
| Explanation: condenser and evaporator. | |
| 94. |
Which of the following operations occur in a vapour refrigeration cycle? |
| A. | compression |
| B. | cooling and condensing |
| C. | expansion and evaporation |
| D. | all of the mentioned |
| Answer» D. all of the mentioned | |
| Explanation: these are the processes which constitute the vapour refrigeration cycle. | |
| 95. |
Compression can be |
| A. | dry compression |
| B. | wet compression |
| C. | both of the mentioned |
| D. | none of the mentioned |
| Answer» C. both of the mentioned | |
| Explanation: dry compression starts with saturated vapour and wet compression starts with wet vapour. | |
| 96. |
Wet compression is preferred over dry compression. |
| A. | true |
| B. | false |
| Answer» B. false | |
| Explanation: dry compression is always preferred. | |
| 97. |
Why is wet compression not preferred? |
| A. | the liquid refrigerant can be trapped in the head of cylinder |
| B. | this may damage the valves or cylinder head |
| C. | liquid refrigerant can wash away the lubricating oil thus accelerating wear |
| D. | all of the mentioned |
| Answer» D. all of the mentioned | |
| Explanation: these are the reasons why dry compression is preferred over wet compression. | |
| 98. |
The expansion process is |
| A. | isentropic |
| B. | reversible |
| C. | adiabatic |
| D. | all of the mentioned |
| Answer» C. adiabatic | |
| Explanation: the expansion process is adiabatic but not isentropic and is irreversible. | |
| 99. |
The evaporation process is a |
| A. | constant volume reversible process |
| B. | constant pressure reversible process |
| C. | adiabatic throttling process |
| D. | reversible adiabatic process |
| Answer» B. constant pressure reversible process | |
| Explanation: this is the last process and it completes the cycle. | |
| 100. |
The evaporator produces the cooling or refrigerating effect. |
| A. | true |
| B. | false |
| Answer» A. true | |
| Explanation: it absorbs heat from the surroundings by evaporation. | |
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