McqMate
These multiple-choice questions (MCQs) are designed to enhance your knowledge and understanding in the following areas: Mechanical Engineering .
Chapters
| 201. |
"The difference between the length of a certain brass rod and that of a steel rod is clamped to be constant at all temperatures". The above statement |
| A. | can never be true |
| B. | can be valid only for temperatures below 0?C |
| C. | can be true provided their lengths are directly proportional to the linear coefficients of the material of the rod |
| D. | can be true provided their lengths are directly proportional to the linear coefficients of the material of the rod |
| E. | None of the above |
| Answer» D. can be true provided their lengths are directly proportional to the linear coefficients of the material of the rod | |
| 202. |
Ten grams of moisture per kg of dry air is removed from atmospheric air during air conditioning and the temperature becomes 30?C. If the atmospheric conditions are 40?C DBT and 60% Relative humidity, the RH of air after refrigeration would be |
| A. | 50% |
| B. | 69% |
| C. | 40% |
| D. | 104% |
| E. | 60% |
| Answer» B. 69% | |
| 203. |
PVC tubes are used for condenser and evaporator when the refrigerant is |
| A. | Freon 12 |
| B. | Freon 22 |
| C. | Ammonia |
| D. | Sulphur dioxide |
| E. | None of the above |
| Answer» E. None of the above | |
| 204. |
Which reciprocating compressor is usually used in domestic refrigerators? |
| A. | Open type |
| B. | Semi-sealed type |
| C. | Hermetically sealed type |
| D. | Any of the above |
| E. | None of the above |
| Answer» C. Hermetically sealed type | |
| 205. |
A Carnot refrigerator extracts 100 kcal of heat per minute from a cold room which is maintained at - 15?C and it is discharged to atmosphere 30C?. The horse power required to run the unit would be |
| A. | More than 6 |
| B. | 2 to 5 |
| C. | 5 to 6 |
| D. | 1.5 to 2 |
| E. | 1 |
| Answer» D. 1.5 to 2 | |
| 206. |
If space occupied by the refrigerating plant and cost is the major consideration, which of the following refrigerant will be preferred? |
| A. | Carbondioxide |
| B. | Sulphur dioxide |
| C. | Mehtyl chloride |
| D. | Ammonia |
| E. | Any of the above |
| Answer» A. Carbondioxide | |
| 207. |
When ammonia is the refrigerant, which of the following will be be the material for pipe through which refrigerant flows? |
| A. | Cast steel or wrought iron |
| B. | Copper |
| C. | PVC |
| D. | Brass |
| E. | Aluminium |
| Answer» A. Cast steel or wrought iron | |
| 208. |
Moisture in Freon refrigeration system causes |
| A. | Ineffective refrigeration |
| B. | Damage to compressor |
| C. | High power consumption |
| D. | Freezing of automatic regulating valve |
| E. | None of the above |
| Answer» D. Freezing of automatic regulating valve | |
| 209. |
Which of the following is not a desirable property of a refrigerant? |
| A. | High critical temperature |
| B. | Low specific heat of liquid |
| C. | Low boiling point |
| D. | High specific volume of air |
| E. | All of the above |
| Answer» D. High specific volume of air | |
| 210. |
A Carnot refrigerator operates between 300.3 K and 273 K. The fraction of cooling effect required as work input is |
| A. | 20% |
| B. | 10% |
| C. | 50% |
| D. | Not possible to find with the data |
| E. | All of the above |
| Answer» B. 10% | |
| 211. |
A thermometer in the compressor discharge line |
| A. | Confirms the flow of refrigerant |
| B. | Indicates the efficiency of cycle |
| C. | Helps in adjusting the compressor performance |
| D. | Shows the heat of refrigerant leaving the cylinder on way to the condenser |
| E. | None of the above |
| Answer» D. Shows the heat of refrigerant leaving the cylinder on way to the condenser | |
| 212. |
Freon 12 is a compound consisting of stoms of |
| A. | Carbon, hydrogen and fluorine |
| B. | Carbon and hydrogen |
| C. | Carbon, hydrogen, fluorine and chlorine |
| D. | Carbon, fluorine and chlorine |
| E. | Carbon, hydrogen and oxygen |
| Answer» D. Carbon, fluorine and chlorine | |
| 213. |
During sensible of cooling of air |
| A. | Wet bulb temperature decreases and relative humidity increases |
| B. | Both wet bulb temperatures as well as relative humidity increase |
| C. | Both humidity ratio as well as relative humidity remain constant |
| D. | Both wet bulb temperature as well as relative humidity decrease |
| E. | Wet bulb temperatures increases and relative humidity decreases |
| Answer» A. Wet bulb temperature decreases and relative humidity increases | |
| 214. |
The type of compressor used in refrigeration system is |
| A. | Reciprocating |
| B. | Centrifugal |
| C. | Rotary sliding vane |
| D. | Rotary screw compressor |
| E. | All of the above |
| Answer» E. All of the above | |
| 215. |
In a refrigeration cycle the heat is rejected by refrigerant at |
| A. | Evaporator |
| B. | Condenser |
| C. | Expansion valve |
| D. | Compressor |
| E. | All of the above |
| Answer» B. Condenser | |
| 216. |
2 HP per ton of refrigeration is required to maintain the temperature of - 40?C in the refrigerator if the refrigeration cycle works on Carnot cycle. The COP of the cycle would be |
| A. | 0.4 |
| B. | 1 |
| C. | 2.38 |
| D. | 5 |
| E. | 4.76 |
| Answer» C. 2.38 | |
| 217. |
An average adult while sitting in a cinema hall |
| A. | Discharges about 100 kcal of heat per hour |
| B. | Discards about 500 kcal of heat per hour |
| C. | Absorbs about 500 kcal of heat per hour |
| D. | Neither absorbs nor discards heat |
| E. | Absorbs about 100 kcal of heat per hour |
| Answer» A. Discharges about 100 kcal of heat per hour | |
| 218. |
During compression in a vapour compression cycle of the refrigerant is super heated |
| A. | C.O.P. is reduced |
| B. | C.O.P. is increased |
| C. | Work done is reduced |
| D. | Refrigerating effect is reduced |
| E. | None of the above |
| Answer» A. C.O.P. is reduced | |
| 219. |
The heat removed capacity of a one ton refrigerator is |
| A. | 100 kcal/4 hour |
| B. | 100 kcal/hour |
| C. | 50 kcal/min |
| D. | 25 kcal/sec |
| E. | None of the above |
| Answer» C. 50 kcal/min | |
| 220. |
A prssure gauge on the discharge side of compressor |
| A. | Is mounted for show only |
| B. | Indicates the temperature of refrigerant after compression |
| C. | Gives a warning when the pressure reaches a dangerous point |
| D. | Gives an ideas about the coefficient of performance of the cycle |
| E. | Confirms the flow of refrigerant in cycle |
| Answer» C. Gives a warning when the pressure reaches a dangerous point | |
| 221. |
Major modification required to produce temperature of - 200?C in a vapour compression refrigeration system using Freon 12 as refrigerant, is |
| A. | Condenser capacity must be increased to handle the refrigerant |
| B. | Size of compressor required would be large to handle volumes of vapour |
| C. | Compression ratio has to be restricted till stronger body of compressor is needed |
| D. | Freon 12 cannot be used for such low temperatures |
| E. | Insulation should be capable of withstanding such low temperatures |
| Answer» D. Freon 12 cannot be used for such low temperatures | |
| 222. |
In a vapour absorption refrigeration system the power is required for vapour compressor as compared to that in vapour compression cycle is |
| A. | More |
| B. | Less |
| C. | There is no such relation |
| D. | One forth |
| E. | Half |
| Answer» C. There is no such relation | |
| 223. |
In a mechanical refrigeration system the refrigerant occurs as liquid (or very wet vapour) between |
| A. | Before and after compressor |
| B. | Expansion valve or evaporator |
| C. | Condenser and expansion valve |
| D. | Evaporation valve and compressor |
| E. | Compressor outlet and condenser |
| Answer» C. Condenser and expansion valve | |
| 224. |
The chemical formula for Freon-12 is |
| A. | CCI2F2 |
| B. | CH3CL |
| C. | CCIF3 |
| D. | CHCIF2 |
| E. | CCIF2CF3 |
| Answer» D. CHCIF2 | |
| 225. |
The ratio of specific humidity of moist air to the specific immidity of the saturated air at the same temperature, is known as |
| A. | Absolute humidity |
| B. | Degree of saturation and degree of reaction |
| C. | Relative humidity |
| D. | Any of the above |
| E. | None of the above |
| Answer» B. Degree of saturation and degree of reaction | |
| 226. |
Dehydration means |
| A. | Removing steam from any matter |
| B. | Removing water from any matter |
| C. | Removing hydrogen from any matter |
| D. | Removing hydrogen from a hydrocarbon |
| E. | Removing hydrogen from a mixture |
| Answer» B. Removing water from any matter | |
| 227. |
Defrosting in a refrigerator may be done by |
| A. | Stopping the compressor for a while |
| B. | Opening the door of refrigerator |
| C. | Placing trays of warm water in the refrigerator |
| D. | Any of the above |
| E. | None of the above |
| Answer» D. Any of the above | |
| 228. |
A cooling tower in a refrigeration system |
| A. | Removes heat from refrigerant |
| B. | Removes heat from brine |
| C. | Removes heat from lubricating oil |
| D. | Removes heat from hot water coming out of condenser |
| E. | None of the above |
| Answer» D. Removes heat from hot water coming out of condenser | |
| 229. |
A hermetic compressor is |
| A. | A reciprocating compressor |
| B. | A valveless compressor |
| C. | A thermodynamically efficient comprossor |
| D. | A factory sealed unit containing motor and compressor |
| E. | None of the above |
| Answer» D. A factory sealed unit containing motor and compressor | |
| 230. |
A refrigerant is added to vapour compression cycle through |
| A. | High side in vapour form |
| B. | High side in liquid form |
| C. | Low side in liquid form |
| D. | None of the above |
| E. | Any of the above |
| Answer» B. High side in liquid form | |
| 231. |
The horse power per ton of refrigerating effect when ammonia is used as a refrigerant, will be nearly |
| A. | 5 |
| B. | 2 |
| C. | 0.1 |
| D. | 0.5 |
| E. | 1 |
| Answer» E. 1 | |
| 232. |
Dalton's law of partial pressure state that |
| A. | All gases exert partial pressures only |
| B. | All gases or mixture of gases exent partial pressures |
| C. | All gases or mixture of gases in a container will exert their own pressure on the container entirely indipendent of the others |
| D. | Total pressure exerted by a mixture of gases or vapours is equal to the pressure exerted by individual gases or vapours |
| E. | None of the above |
| Answer» C. All gases or mixture of gases in a container will exert their own pressure on the container entirely indipendent of the others | |
| 233. |
When moisture is removed from air at constant dry bulb temperature the process is known as |
| A. | Drying |
| B. | Sensible cooling |
| C. | Aeration |
| D. | Deionisation |
| E. | Dehumidification |
| Answer» E. Dehumidification | |
| 234. |
In a newly charged ammonia compression system, the clicking sound in the expansion valve indicates |
| A. | High pressure after compression |
| B. | Leakage of ammonia |
| C. | Excessive ammonia charged |
| D. | Lack of ammonia |
| E. | Evaporator coils chocked |
| Answer» D. Lack of ammonia | |
| 235. |
The difference between wet and dry bulb temperature |
| A. | Increases at atmospheric temperature |
| B. | Increases as air gets wet |
| C. | Increases as air gets drier |
| D. | Remains constant always |
| E. | None of the above |
| Answer» C. Increases as air gets drier | |
| 236. |
For better performance a desert cooler |
| A. | Should be placed inside the room |
| B. | Should be placed outside |
| C. | Should be mounted on window |
| D. | Should be placed at the roof level |
| E. | None of the above |
| Answer» C. Should be mounted on window | |
| 237. |
Which of the following are synonyms? |
| A. | Humidity ratio and specific humidity |
| B. | Degree of saturation and degree of reaction |
| C. | Sensible cooling and dehumidification |
| D. | Relative humidity and specific humidity |
| E. | Dehumidification |
| Answer» A. Humidity ratio and specific humidity | |
| 238. |
At 100% humidity |
| A. | We bulb temperature is same as atmospheric temperature |
| B. | Dry bulb temperature is same as atmospheric temperature |
| C. | Wet bulb temperature is same as dry bulb temperature |
| D. | Dry bulb temperature is exactly half the wet bulb temperature |
| E. | Wet bulb temperature is exactly half the dry bulb temperature |
| Answer» C. Wet bulb temperature is same as dry bulb temperature | |
| 239. |
Which of the following symptoms will indicate under charging of a vapour compressor refrigeration cycle? |
| A. | Compressor runs continuously |
| B. | Frost on suction line |
| C. | Low suction pressure |
| D. | Low head pressure |
| E. | All of the above |
| Answer» B. Frost on suction line | |
| 240. |
The drift loss in cooling towers is around |
| A. | 40 to 50% |
| B. | 1% |
| C. | 10 to 20% |
| D. | 2 to 5% |
| E. | 30 to 35% |
| Answer» C. 10 to 20% | |
| 241. |
Cooling towers are used for cooling water |
| A. | To be used for cooling the compressor |
| B. | To be used for filtration of air |
| C. | To be injected in circulating air |
| D. | To be used for humidification |
| E. | To be used for cooling the building |
| Answer» A. To be used for cooling the compressor | |
| 242. |
Refrigerant 744 is |
| A. | Carbondioxide |
| B. | Freon 22 |
| C. | Freon 12 |
| D. | Air |
| E. | Ammonia |
| Answer» A. Carbondioxide | |
| 243. |
In a ammonia vapour compression cycle during gas charging the connection is made |
| A. | Anywhere in the cycle |
| B. | At the compressor cycle |
| C. | On low pressure side near evaporat |
| D. | At the compressor outlet |
| E. | On high pressure side close to receiver |
| Answer» E. On high pressure side close to receiver | |
| 244. |
In central air conditioning system |
| A. | Entire equipment is placed in the air conditioned space |
| B. | There is only one machine which performs the function of air conditioning |
| C. | All the major equipment is located in one central space removed from the air to be conditioned |
| D. | Is used when small area is to be air conditioned |
| E. | None of the above |
| Answer» C. All the major equipment is located in one central space removed from the air to be conditioned | |
| 245. |
A refrigerant cycle is usually a |
| A. | Open cycle |
| B. | Closed cycle |
| C. | Mixed cycle |
| D. | Hybrid cycle |
| E. | None of the above |
| Answer» B. Closed cycle | |
| 246. |
Refrigerant R-40 is |
| A. | Air |
| B. | Methyl chloride |
| C. | Glycol |
| D. | Brine |
| E. | None of the above |
| Answer» B. Methyl chloride | |
| 247. |
In order to ensure leak proof mechanical links, the end of copper tubing in refrigeration cycle is |
| A. | Flared |
| B. | Brazed |
| C. | Soldered |
| D. | Press-fitted |
| E. | (C) and (D) together |
| Answer» A. Flared | |
| 248. |
A Bell-Coleman cycle is |
| A. | Reversed Otto cycle |
| B. | Reversed Carnot cycle |
| C. | Reversed Sterling cycle |
| D. | Reversed Joule cycle |
| E. | Reversed Rankine cycle |
| Answer» D. Reversed Joule cycle | |
| 249. |
On a particular time of a day if dry bulb temperature is equal to the wet bulb temperature, then it can be safely concluded that |
| A. | Dew point was less than 20?C |
| B. | Rain had occurred one or two hours earlier |
| C. | Relative humidity of air was 100% |
| D. | Specific humidity of air was 0.010 kg per kg of dry air |
| E. | Atmospheric air was free from moisture |
| Answer» C. Relative humidity of air was 100% | |
| 250. |
Which of the following is not a dehydrator? |
| A. | Silica sel |
| B. | Molecular sieve |
| C. | Calcium chloride |
| D. | Sodium chloride |
| E. | All of the above |
| Answer» E. All of the above | |
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