MCQOPTIONS
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MCQOPTIONS
This section includes 265 Mcqs, each offering curated multiple-choice questions to sharpen your Mechanical Engineering knowledge and support exam preparation. Choose a topic below to get started.
| 201. |
The critical temperature is the temperature |
| A. | below which a gas does not obey gas laws |
| B. | above which a gas may explode |
| C. | below which a gas is always liquified |
| D. | above which a gas will never liquified |
| Answer» E. | |
| 202. |
For air conditioning the operation theatre in a hospital, the percentage of outside air in the air supplied is |
| A. | zero |
| B. | 20 |
| C. | 50 |
| D. | 100 |
| Answer» E. | |
| 203. |
In case ofsensible cooling of air, the coil efficiency is given by |
| A. | B.P.F. - 1 |
| B. | 1 - B.P.F. |
| C. | 1 + B.P.F. |
| Answer» C. 1 + B.P.F. | |
| 204. |
The cooling system used for supersonic aircrafts and rockets is |
| A. | simple air cooling system |
| B. | boot-strap air cooling system |
| C. | reduced ambient air cooling system |
| D. | regenerative air cooling system |
| Answer» E. | |
| 205. |
The desirable property of a refrigerant is |
| A. | low boiling point |
| B. | high critical temperature |
| C. | high latent heat of vaporisation |
| D. | all of these |
| Answer» E. | |
| 206. |
The wet bulb depression indicates __________ humidity of the air. |
| A. | absolute |
| B. | relative |
| C. | specific |
| Answer» C. specific | |
| 207. |
The refrigerant widely used in domestic refrigerators is |
| A. | ammonia |
| B. | carbon dioxide |
| C. | sulphur dioxide |
| D. | R-12 |
| Answer» E. | |
| 208. |
When absorptivity (α) = 1, reflectivity (ρ) = 0 and transmittivity (τ) = 0, then the body is said to be a |
| A. | black body |
| B. | grey body |
| C. | opaque body |
| D. | white body |
| Answer» B. grey body | |
| 209. |
Prandtl number () is given by = μ./. |
| A. | Yes |
| B. | No |
| Answer» B. No | |
| 210. |
The humidification process, on the psychrometric chart is shown by |
| A. | horizontal line |
| B. | vertical line |
| C. | inclined line |
| D. | curved line |
| Answer» C. inclined line | |
| 211. |
The colour of the flame of halide torch, in case of leakage of freon refrigerant, will change to |
| A. | bright green |
| B. | yellow |
| C. | red |
| D. | orange |
| Answer» B. yellow | |
| 212. |
Air refrigerator works on |
| A. | reversed Carnot cycle |
| B. | Bell Coleman cycle |
| C. | both (a) and ib) |
| D. | none of these |
| Answer» D. none of these | |
| 213. |
The reciprocating refrigerant compressors are very suitable for |
| A. | small displacements and low condensing pressures |
| B. | large displacements and high condensing pressures |
| C. | small displacements and high condensing pressures |
| D. | large displacements and low condensing pressures |
| Answer» D. large displacements and low condensing pressures | |
| 214. |
The boiling point of carbon dioxide is |
| A. | -20.5°C |
| B. | -50°C |
| C. | -63.3°C |
| D. | -78.3°C |
| Answer» E. | |
| 215. |
The relative coefficient of performance is equal to |
| A. | Actual C.O.P. x Theoretical C.O.P. |
| B. | none of these |
| Answer» C. | |
| 216. |
The mass of water vapour present in 1 kg of dry air, is called humidity ratio. |
| A. | True |
| B. | False |
| Answer» B. False | |
| 217. |
In a vapour compression refrigeration system, a throttle valve is used in place of an expander because |
| A. | it considerably reduces mass of the system |
| B. | it improves the C.O.P., as the condenser is small |
| C. | the positive work in isentropic expansion of liquid is very small |
| D. | it leads to significant cost reduction |
| Answer» D. it leads to significant cost reduction | |
| 218. |
For large tonnage (more than 200 TR) air-conditioning applications, the compressor recommended is |
| A. | reciprocating |
| B. | rotating |
| C. | centrifugal |
| D. | screw |
| Answer» D. screw | |
| 219. |
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, is called |
| A. | humidity ratio |
| B. | relative humidity |
| C. | absolute humidity |
| D. | degree of saturation |
| Answer» C. absolute humidity | |
| 220. |
During dehumidification process, the relative humidity |
| A. | remains constant |
| B. | increases |
| C. | decreases |
| Answer» D. | |
| 221. |
The space between the two walls of a thermos flask is evacuated because vacuum is a __________ conductor of heat. |
| A. | good |
| B. | bad |
| Answer» C. | |
| 222. |
The ratio of actual heat transfer to the maximum possible heat transfer is known as heat exchanger effectiveness. |
| A. | Agree |
| B. | Disagree |
| Answer» B. Disagree | |
| 223. |
The ratio of heat extracted in the refrigerator to the workdone 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 | |
| 224. |
Dry bulb temperature is the temperature of air recorded by a thermometer, when |
| A. | it is not affected by the moisture present in the air |
| B. | its bulb is surrounded by a wet cloth exposed to the air |
| C. | the moisture present in it begins to condense |
| D. | none of the above |
| Answer» B. its bulb is surrounded by a wet cloth exposed to the air | |
| 225. |
In a spray washing system, if the temperature of water is higher than the dry bulb temperature of entering air, then the air is |
| A. | heated and dehumidified |
| B. | heated and humidified |
| C. | cooled and humidified |
| D. | cooled and dehumidified |
| Answer» C. cooled and humidified | |
| 226. |
The atmospheric air at dry bulb temperature of 15°C enters a heating coil maintained at 40°C. The air leaves the heating coil at 25°C. The by-pass factor of the heating coil is |
| A. | 0.376 |
| B. | 0.4 |
| C. | 0.6 |
| D. | 0.67 |
| Answer» D. 0.67 | |
| 227. |
An infinite parallel planes with emissivities and , the interchange factor for radiation from surface 1 to surface 2 is given by |
| A. | + |
| Answer» B. | |
| 228. |
The dry bulb temperature lines, on the psychrometric chart are |
| A. | vertical and uniformly spaced |
| B. | horizontal and uniformly spaced |
| C. | horizontal and non-uniformly spaced |
| D. | curved lines |
| Answer» B. horizontal and uniformly spaced | |
| 229. |
The pressure at the outlet of a refrigerant compressor is called |
| A. | suction pressure |
| B. | discharge pressure |
| C. | critical pressure |
| D. | back pressure |
| Answer» C. critical pressure | |
| 230. |
A simple air cooling system is good for __________ flight speeds. |
| A. | low |
| B. | high |
| Answer» B. high | |
| 231. |
The __________ point of ammonia is -77.7°C. |
| A. | freezing |
| B. | boiling |
| Answer» B. boiling | |
| 232. |
Sulphur dioxide has the lowest boiling point. |
| A. | Yes |
| B. | No |
| Answer» C. | |
| 233. |
In a psychrometric chart, dew point temperature lines are horizontal and non-uniformly spaced. |
| A. | Correct |
| B. | Incorrect |
| Answer» B. Incorrect | |
| 234. |
If the evaporator temperature is kept constant, the coefficient of performance of a refrigeration cycle __________ with the increase in condenser temperature. |
| A. | increases |
| B. | decreases |
| Answer» C. | |
| 235. |
The evaporator used in house-hold refrigerators is |
| A. | frosting evaporator |
| B. | non-frosting evaporator |
| C. | defrosting evaporator |
| D. | none of these |
| Answer» B. non-frosting evaporator | |
| 236. |
The drier in a refrigeration system removes moisture in the system. |
| A. | Correct |
| B. | Incorrect |
| Answer» B. Incorrect | |
| 237. |
For a given dry bulb temperature, as the relative humidity __________ the wet bulb temperature will increase. |
| A. | increases |
| B. | decreases |
| Answer» C. | |
| 238. |
A low wet bulb temperature indicates very __________ humidity. |
| A. | low |
| B. | high |
| Answer» B. high | |
| 239. |
The operating temperature of a cold storage is - 2° C. The heat leakage from the surrounding is 30 kW for the ambient temperature of 40° C. The actual C.O.P. of refrigeration plant used is one fourth that of ideal plant working between the same temperatures. The power required to drive the plant is |
| A. | 1.86 kW |
| B. | 3.72 kW |
| C. | 7.44 kW |
| D. | 18.6 kW |
| Answer» E. | |
| 240. |
In chemical dehumidification process, |
| A. | dew point temperature decreases |
| B. | wet bulb temperature decreases |
| C. | dry bulb temperature increases |
| D. | all of these |
| Answer» E. | |
| 241. |
The air cooling system mostly used in transport type aircrafts is |
| A. | simple air cooling system |
| B. | simple evaporative air cooling system |
| C. | boot-strap air cooling system |
| D. | all of these |
| Answer» D. all of these | |
| 242. |
The critical thickness of insulation is the ratio of thermal conductivity of the insulating material (k) to the heat transfer coefficient at the outer surface of the insulation (). |
| A. | True |
| B. | False |
| Answer» B. False | |
| 243. |
In counter-current flow heat exchanger, the logarithmic temperature difference between the fluids is __________ as compared to parallel flow heat exchanger. |
| A. | same |
| B. | less |
| C. | greater |
| Answer» D. | |
| 244. |
Environmental protection agencies advice against the use of chloro-fluoro-carbon refrigerants since |
| A. | these react with water vapour and cause acid rain |
| B. | these react with plants and cause green-house effect |
| C. | these react with oxygen and cause its depletion |
| D. | these react with ozone layer |
| Answer» E. | |
| 245. |
The refrigerant carbon dioxide is not widely used because of its __________ power require ments per tonne of refrigeration and high operating pressures. |
| A. | low |
| B. | high |
| Answer» C. | |
| 246. |
The by-pass 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 | |
| 247. |
During dehumidification process, __________ remains constant. |
| A. | wet bulb temperature |
| B. | relative humidity |
| C. | dry bulb temperature |
| D. | specific humidity |
| Answer» D. specific humidity | |
| 248. |
Pressure of water vapour is given by |
| A. | none of these |
| Answer» E. | |
| 249. |
A thermostatic expansion valve in a refrigeration system |
| A. | ensures the evaporator completely filled with refrigerant of the load |
| B. | is suitable only for constant load systems |
| C. | maintains different temperatures in evaporator in proportion to load |
| D. | none of the above |
| Answer» B. is suitable only for constant load systems | |
| 250. |
The temperature rise, between the condenser outlet and expansion valve in ammonia vapour compression system, should be as low as possible. |
| A. | Yes |
| B. | No |
| Answer» B. No | |