MCQOPTIONS
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MCQOPTIONS
This section includes 346 Mcqs, each offering curated multiple-choice questions to sharpen your GATE (Mechanical Engineering) knowledge and support exam preparation. Choose a topic below to get started.
| 201. |
Degree of saturation or percentage humidity is |
| A. | The mass of water vapour present in 1 m³ of dry air |
| B. | The mass of water vapour present in 1 kg of dry air |
| C. | The ratio of the actual mass of water vapour in a unit mass of dry air to the mass of water vapour in the same mass of dry air when it is saturated at the same temperature and pressure |
| D. | The ratio of actual mass of water vapour in a given volume of moist air to the mass of water vapour in the same volume of saturated air at the same temperature and pressure |
| Answer» D. The ratio of actual mass of water vapour in a given volume of moist air to the mass of water vapour in the same volume of saturated air at the same temperature and pressure | |
| 202. |
In larger industrial and commercial reciprocating compression systems, refrigerant widely used is |
| A. | Ammonia |
| B. | Carbon dioxide |
| C. | Sulphur dioxide |
| D. | R-12 |
| Answer» B. Carbon dioxide | |
| 203. |
A heat pump working on a reversed Carnot cycle has a C.O.P. of 5. It works as a refrigerator taking 1 kW of work input. The refrigerating effect will be |
| A. | 1 kW |
| B. | 2 kW |
| C. | 3 kW |
| D. | 4 kW |
| Answer» E. | |
| 204. |
The capillary tube is not used in large capacity refrigeration systems because |
| A. | Cost is too high |
| B. | Capacity control is not possible |
| C. | It is made of copper |
| D. | Required pressure drop cannot be achieved |
| Answer» C. It is made of copper | |
| 205. |
In actual air-conditioning applications for R-12 and R-22, and operating at a condenser temperature of 40° C and an evaporator temperature of 5° C, the heat rejection factor is about |
| A. | 1 |
| B. | 1.25 |
| C. | 2.15 |
| D. | 5.12 |
| Answer» C. 2.15 | |
| 206. |
Highest temperature encountered in refrigeration cycle should be |
| A. | Near critical temperature of refrigerant |
| B. | Above critical temperature |
| C. | At critical Temperature |
| D. | Much below critical temperature |
| Answer» E. | |
| 207. |
The higher temperature in vapour compression cycle occurs at |
| A. | Receiver |
| B. | Expansion valve |
| C. | Evaporator |
| D. | Compressor discharge |
| Answer» E. | |
| 208. |
The leaks in a refrigeration system using Freon are detected by |
| A. | Halide torch which on detection produces greenish flame lighting |
| B. | Sulphur sticks which on detection gives white smoke |
| C. | Using reagents |
| D. | Smelling |
| Answer» B. Sulphur sticks which on detection gives white smoke | |
| 209. |
The advantage of dry compression is that |
| A. | It permits higher speeds to be used |
| B. | It permits complete evaporation in the evaporator |
| C. | It results in high volumetric and mechanical efficiency |
| D. | All of the above |
| Answer» E. | |
| 210. |
If a gas is to be liquefied, its temperature must be |
| A. | Increased to a value above its critical temperature |
| B. | Reduced to a value below its critical temperature |
| C. | Equal to critical temperature |
| D. | None of the above |
| Answer» D. None of the above | |
| 211. |
The relative coefficient of performance is equal to |
| A. | (Theoretical C.O.P.)/ (Actual C.O.P.) |
| B. | (Actual C.O.P.) /(Theoretical C.O.P.) |
| C. | (Actual C.O.P.) × (Theoretical C.O.P.) |
| D. | None of these |
| Answer» C. (Actual C.O.P.) × (Theoretical C.O.P.) | |
| 212. |
The C.O.P. of a refrigerator working on a reversed Carnot cycle is (where T₁ = Lowest absolute temperature, and T₂ = Highest absolute temperature) |
| A. | T₁ / (T₂ - T₁) |
| B. | (T₂ - T₁)/T₁ |
| C. | (T₁ - T₂)/T₁ |
| D. | T₂/ (T₂ - T₁) |
| Answer» B. (T₂ - T₁)/T₁ | |
| 213. |
The wet bulb temperature during sensible heating of air |
| A. | Remains constant |
| B. | Increases |
| C. | Decreases |
| D. | None of these |
| Answer» C. Decreases | |
| 214. |
The dry bulb temperature during sensible heating of air |
| A. | Remains constant |
| B. | Increases |
| C. | Decreases |
| D. | None of these |
| Answer» C. Decreases | |
| 215. |
The wet bulb temperature during sensible cooling of air |
| A. | Remains constant |
| B. | Increases |
| C. | Decreases |
| D. | None of these |
| Answer» D. None of these | |
| 216. |
The relative humidity is defined as |
| A. | The mass of water vapour present in 1 m3 of dry air |
| B. | The mass of water vapour present in 1 kg of dry air |
| C. | The ratio of the actual mass of water vapour in a unit mass of dry air to the mass of water vapour in the same mass of dry air when it is saturated at the same temperature and pressure |
| D. | The ratio of actual mass of water vapour in a given volume of moist air to the mass of water vapour in the same volume of saturated air at the same temperature and pressure |
| Answer» E. | |
| 217. |
A refrigerating system operating on reversed Brayton refrigeration cycle is used for maintaining 250 K. If the temperature at the end of constant pressure cooling is 300 K and rise in the temperature of air in the refrigerator is 50 K, then the net work of compression will be (assume air as working substance with Cp = 1 kJ/kg) |
| A. | 25 kJ/kg |
| B. | 50 kJ/kg |
| C. | 100 kJ/kg |
| D. | 125 kJ/kg |
| Answer» C. 100 kJ/kg | |
| 218. |
Moisture in Freon refrigeration system causes |
| A. | Ineffective refrigeration |
| B. | High power consumption |
| C. | Freezing automatic regulating valve |
| D. | Corrosion of whole system |
| Answer» D. Corrosion of whole system | |
| 219. |
The boiling point of ammonia is |
| A. | -10.5°C |
| B. | -30°C |
| C. | -33.3°C |
| D. | -77.7°C |
| Answer» D. -77.7°C | |
| 220. |
The formation of frost on cooling coils in a refrigerator |
| A. | Increases heat transfer |
| B. | Improves C.O.P. of the system |
| C. | Increases power consumption |
| D. | Reduces power consumption |
| Answer» D. Reduces power consumption | |
| 221. |
The bypass factor of a cooling coil decreases with |
| A. | Decrease in fin spacing and increase in number of rows |
| B. | Increase in fin spacing and increase in number of rows |
| C. | Increase in fin spacing and decrease in number of rows |
| D. | Decrease in fin spacing and decrease in number of rows |
| Answer» B. Increase in fin spacing and increase in number of rows | |
| 222. |
Air refrigerator works on |
| A. | Reversed Carnot cycle |
| B. | Bell Coleman cycle |
| C. | Both (A) and (B) |
| D. | None of these |
| Answer» D. None of these | |
| 223. |
Moisture should be removed from refrigerants to avoid |
| A. | Freezing at the expansion valve |
| B. | Restriction to refrigerant flow |
| C. | Corrosion of steel plates |
| D. | All of these |
| Answer» E. | |
| 224. |
The vapour pressure of refrigerant should be |
| A. | Lower than atmospheric pressure |
| B. | Higher than atmospheric pressure |
| C. | Equal to atmospheric pressure |
| D. | Could be anything |
| Answer» C. Equal to atmospheric pressure | |
| 225. |
The material of pipe lines for a system using Freon as a refrigerant should be |
| A. | Brass |
| B. | Copper |
| C. | Steel |
| D. | Aluminium |
| Answer» C. Steel | |
| 226. |
The ratio of heat extracted in the refrigerator to the work-done on the refrigerant is called |
| A. | Coefficient of performance of refrigeration |
| B. | Coefficient of performance of heat pump |
| C. | Relative coefficient of performance |
| D. | Refrigerating efficiency |
| Answer» B. Coefficient of performance of heat pump | |
| 227. |
The specific humidity during humidification process |
| A. | Remains constant |
| B. | Increases |
| C. | Decreases |
| D. | None of these |
| Answer» C. Decreases | |
| 228. |
The specific humidity during dehumidification process |
| A. | Remains constant |
| B. | Increases |
| C. | Decreases |
| D. | None of these |
| Answer» D. None of these | |
| 229. |
A standard ice point temperature corresponds to the temperature of |
| A. | Water at 0°C |
| B. | Ice at 4°C |
| C. | Solid and dry ice |
| D. | Mixture of ice and water under equilibrium conditions |
| Answer» E. | |
| 230. |
A condenser of refrigeration system rejects heat at the rate of 120 kW, while its compressor consumes a power of 30 kW. The coefficient of performance of the system will be |
| A. | 1/4 |
| B. | 1/3 |
| C. | 3 |
| D. | 4 |
| Answer» E. | |
| 231. |
The thermostatic expansion valve operates on the changes in the |
| A. | Degree of superheat at exit from the evaporator |
| B. | Temperature of the evaporator |
| C. | Pressure in the evaporator |
| D. | None of the above |
| Answer» B. Temperature of the evaporator | |
| 232. |
The temperature of air recorded by a thermometer, when its bulb is surrounded by a wet cloth exposed to the air, is called |
| A. | Wet bulb temperature |
| B. | Dry bulb temperature |
| C. | Dew point temperature |
| D. | None of these |
| Answer» B. Dry bulb temperature | |
| 233. |
The temperature of air recorded by a thermometer, when it is not affected by the moisture present in the air, is called |
| A. | Wet bulb temperature |
| B. | Dry bulb temperature |
| C. | Dew point temperature |
| D. | None of these |
| Answer» C. Dew point temperature | |
| 234. |
In case of sensible cooling of air, the coil efficiency is given by |
| A. | B.P.F. - 1 |
| B. | 1 - B.P.F. |
| C. | 1/ B.P.F. |
| D. | 1 + B.P.F. |
| Answer» C. 1/ B.P.F. | |
| 235. |
The wet bulb depression indicates _________ humidity of the air. |
| A. | Absolute |
| B. | Relative |
| C. | Specific |
| D. | None of these |
| Answer» C. Specific | |
| 236. |
Which of the following refrigerant is highly toxic and flammable? |
| A. | Ammonia |
| B. | Carbon dioxide |
| C. | Sulphur dioxide |
| D. | R-12 |
| Answer» B. Carbon dioxide | |
| 237. |
The lower horizontal line of the refrigeration cycle plotted on pressure-enthalpy diagram represents |
| A. | Condensation of the refrigerant vapour |
| B. | Evaporation of the refrigerant liquid |
| C. | Compression of the refrigerant vapour |
| D. | Metering of the refrigerant liquid |
| Answer» C. Compression of the refrigerant vapour | |
| 238. |
The leakage in a refrigeration system using ammonia is detected by |
| A. | Halide torch |
| B. | Sulphur sticks |
| C. | Soap and water |
| D. | All of these |
| Answer» C. Soap and water | |
| 239. |
Air refrigeration cycle is used in |
| A. | Domestic refrigerators |
| B. | Commercial refrigerators |
| C. | Air conditioning |
| D. | Gas liquefaction |
| Answer» E. | |
| 240. |
The minimum temperature to which water can be cooled in a cooling tower is |
| A. | Dew point temperature of air |
| B. | Wet bulb temperature of air |
| C. | Dry bulb temperature of air |
| D. | Ambient air temperature |
| Answer» C. Dry bulb temperature of air | |
| 241. |
In refrigerators, the temperature difference between the evaporating refrigerant and the medium being cooled should be |
| A. | High, of the order of 25° |
| B. | As low as possible (3 to 11°C) |
| C. | Zero |
| D. | Any value |
| Answer» C. Zero | |
| 242. |
In a domestic vapour compression refrigerator, the refrigerant commonly used is |
| A. | CO? |
| B. | Ammonia |
| C. | R-12 |
| D. | All of these |
| Answer» D. All of these | |
| 243. |
During cooling and dehumidification, dry bulb temperature |
| A. | Remains constant |
| B. | Increases |
| C. | Decreases |
| D. | None of these |
| Answer» D. None of these | |
| 244. |
The process, generally used in summer air conditioning to cool and dehumidify the air, is called |
| A. | Humidification |
| B. | Dehumidification |
| C. | Heating and humidification |
| D. | Cooling and dehumidification |
| Answer» E. | |
| 245. |
The process, generally used in winter air-conditioning to warm and humidity the air, is called |
| A. | Humidification |
| B. | Dehumidification |
| C. | Heating and humidification |
| D. | Cooling and dehumidification |
| Answer» D. Cooling and dehumidification | |
| 246. |
The dehumidification process, on the psychrometric chart, is shown by |
| A. | Horizontal line |
| B. | Vertical line |
| C. | Inclined line |
| D. | Curved line |
| Answer» C. Inclined line | |
| 247. |
Hydrogen is used in Electrolux refrigeration system so as to _________ the rate of evaporation of the liquid ammonia passing through the evaporator. |
| A. | Equalize |
| B. | Reduce |
| C. | Increase |
| D. | None of these |
| Answer» D. None of these | |
| 248. |
Superheating in a refrigeration cycle |
| A. | Increases C.O.P |
| B. | Decreases C.O.P |
| C. | C.O.P remains unaltered |
| D. | Other factors decide C.O.P |
| Answer» C. C.O.P remains unaltered | |
| 249. |
Under cooling in a refrigeration cycle |
| A. | Increases C.O.P |
| B. | Decreases C.O.P |
| C. | C.O.P remains unaltered |
| D. | Other factors decide C.O.P |
| Answer» B. Decreases C.O.P | |
| 250. |
The superheating in a refrigeration cycle |
| A. | Does not alter C.O.P. |
| B. | Increases C.O.P. |
| C. | Decreases C.O.P. |
| D. | None of these |
| Answer» D. None of these | |