MCQOPTIONS
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MCQOPTIONS
This section includes 368 Mcqs, each offering curated multiple-choice questions to sharpen your Mechanical Engineering knowledge and support exam preparation. Choose a topic below to get started.
| 301. |
In a saturated air-water vapour mixture, the |
| A. | Dry bulb temperature is higher than wet bulb temperature |
| B. | Dew point temperature is lower than wet bulb temperature |
| C. | Dry bulb, wet bulb and dew point temperature are same |
| D. | Dry bulb temperature is higher than dew point temperature |
| Answer» D. Dry bulb temperature is higher than dew point temperature | |
| 302. |
In a vapour compression cycle, the refrigerant immediately after expansion valve is |
| A. | Liquid |
| B. | Sub-cooled liquid |
| C. | Saturated liquid |
| D. | Wet vapour |
| Answer» E. | |
| 303. |
If a heat pump cycle operates between the condenser temperature of +27°C and evaporator temperature of -23°C, then the Carnot COP will be$ |
| A. | 0.2 |
| B. | 1.2 |
| C. | 5 |
| D. | 6 |
| Answer» E. | |
| 304. |
The evaporator changes the low pressure liquid refrigerant from the expansion valve into |
| A. | High pressure liquid refrigerant |
| B. | Low pressure liquid and vapour refrigerant |
| C. | Low pressure vapour refrigerant |
| D. | None of these |
| Answer» D. None of these | |
| 305. |
A one tonne refrigerating machine means that |
| A. | One tonne is the total mass of machine |
| B. | One tonne refrigerant is used |
| C. | One tonne of water can be converted into ice |
| D. | One tonne of ice when melts from and at 0° C in 24 hours, the refrigeration effect is equivalent to 210 kJ/min |
| Answer» E. | |
| 306. |
During sensible heating of air _________ decreases. |
| A. | Wet bulb temperature |
| B. | Relative humidity |
| C. | Dry bulb temperature |
| D. | Specific humidity |
| Answer» C. Dry bulb temperature | |
| 307. |
In a vapour compression system, the condition of refrigerant before passing through the condenser is |
| A. | Saturated liquid |
| B. | Wet vapour |
| C. | Dry saturated vapour |
| D. | Superheated vapour |
| Answer» E. | |
| 308. |
In a vapour compression system, the condition of refrigerant is dry saturated vapour |
| A. | Before entering the compressor |
| B. | After leaving the compressor |
| C. | Before entering the condenser |
| D. | After leaving the condenser |
| Answer» B. After leaving the compressor | |
| 309. |
The evaporator used in household refrigerators is |
| A. | Frosting evaporator |
| B. | Non-frosting evaporator |
| C. | Defrosting evaporator |
| D. | None of these |
| Answer» B. Non-frosting evaporator | |
| 310. |
Freon group of refrigerants are |
| A. | Inflammable |
| B. | Toxic |
| C. | Non-inflammable and toxic |
| D. | Nontoxic and non-inflammable |
| Answer» E. | |
| 311. |
The bypass factor (B. P. F.) in case of sensible heating of air is (Where td‚ÇÅ = Dry bulb temperature of air entering the heating coil, td‚ÇÇ = Dry bulb temperature of air leaving the heating coil, and td‚ÇÉ = Dry bulb temperature of heating coil)$ |
| A. | (td‚ÇÇ - td‚ÇÉ)/(td‚ÇÉ - td‚ÇÅ) |
| B. | (td‚ÇÉ - td‚ÇÇ)/(td‚ÇÉ - td‚ÇÅ) |
| C. | (td‚ÇÉ - td‚ÇÅ)/(td‚ÇÇ - td‚ÇÉ) |
| D. | (td‚ÇÉ - td‚ÇÅ)/(td‚ÇÉ - td‚ÇÇ) |
| Answer» C. (td‚Äö√á√â - td‚Äö√á√Ö)/(td‚Äö√á√á - td‚Äö√á√â) | |
| 312. |
The specific humidity during cooling and dehumidification |
| A. | Remains constant |
| B. | Increases |
| C. | Decreases |
| D. | None of these |
| Answer» D. None of these | |
| 313. |
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 | |
| 314. |
The coefficient of performance of a domestic refrigerator is ________ as compared to a domestic air-conditioner. |
| A. | Same |
| B. | Less |
| C. | More |
| D. | None of these |
| Answer» C. More | |
| 315. |
The freezing point of sulphur dioxide is |
| A. | -56.6°C |
| B. | -75.2°C |
| C. | -77.7°C |
| D. | -135.8°C |
| Answer» C. -77.7¬¨‚àûC | |
| 316. |
A refrigerant with the highest critical pressure is |
| A. | R-11 |
| B. | R-12 |
| C. | R-22 |
| D. | Ammonia |
| Answer» E. | |
| 317. |
During sensible cooling of air, specific humidity |
| A. | Remains constant |
| B. | Increases |
| C. | Decreases |
| D. | None of these |
| Answer» B. Increases | |
| 318. |
In air-conditioning of aeroplanes, using air as a refrigerant, the cycle used is |
| A. | Reversed Carnot cycle |
| B. | Reversed Joule cycle |
| C. | Reversed Brayton cycle |
| D. | Reversed Otto cycle |
| Answer» D. Reversed Otto cycle | |
| 319. |
Which of the following refrigerant has the lowest freezing point? |
| A. | R-11 |
| B. | R-12 |
| C. | R-22 |
| D. | Ammonia |
| Answer» D. Ammonia | |
| 320. |
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 | |
| 321. |
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 | |
| 322. |
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. | |
| 323. |
The specific humidity during dehumidification process |
| A. | Remains constant |
| B. | Increases |
| C. | Decreases |
| D. | None of these |
| Answer» D. None of these | |
| 324. |
One ton refrigeration corresponds to |
| A. | 50 kcal/ min |
| B. | 50 kcal/ hr |
| C. | 80 kcal/ min |
| D. | 80 kcal/ hr |
| Answer» B. 50 kcal/ hr | |
| 325. |
Air conditioning means |
| A. | Cooling |
| B. | Heating |
| C. | Dehumidifying |
| D. | All of these |
| Answer» E. | |
| 326. |
One ton of refrigeration is equal to the refrigeration effect corresponding to melting of 1000 kg of ice |
| A. | In 1 hour |
| B. | In 1 minute |
| C. | In 24 hours |
| D. | In 12 hours |
| Answer» D. In 12 hours | |
| 327. |
In Electrolux refrigerator |
| A. | Ammonia is absorbed in hydrogen |
| B. | Ammonia is absorbed in water |
| C. | Ammonia evaporates in hydrogen |
| D. | Hydrogen evaporates in ammonia |
| Answer» D. Hydrogen evaporates in ammonia | |
| 328. |
Most thermostatic expansion valves are set for a superheat of |
| A. | 5°C |
| B. | 10°C |
| C. | 15°C |
| D. | 20°C |
| Answer» B. 10¬¨‚àûC | |
| 329. |
The bank of tubes at the back of domestic refrigerator is |
| A. | Condenser tubes |
| B. | Evaporator tubes |
| C. | Refrigerant cooling tubes |
| D. | Capillary tubes |
| Answer» B. Evaporator tubes | |
| 330. |
The wet bulb temperature at 100% relative humidity is ________ dry bulb temperature. |
| A. | Same as |
| B. | Lower than |
| C. | Higher than |
| D. | None of these |
| Answer» B. Lower than | |
| 331. |
The index which correlates the combined effects of air temperature, relative humidity and air velocity on the human body, is known as |
| A. | Mean radiant temperature |
| B. | Effective temperature |
| C. | Dew point temperature |
| D. | None of these |
| Answer» C. Dew point temperature | |
| 332. |
While designing the refrigeration system of an aircraft, the prime consideration is that the |
| A. | System has high C.O.P. |
| B. | Power per TR is low |
| C. | Mass of refrigerant circulated in the system is low |
| D. | Mass of the refrigeration equipment is low |
| Answer» E. | |
| 333. |
During heating and humidification, the final relative humidity of air |
| A. | Can be lower or higher than that of the entering air |
| B. | Is lower than that of the entering air |
| C. | Is higher than that of the entering air |
| D. | None of the above |
| Answer» B. Is lower than that of the entering air | |
| 334. |
The lowest thermal diffusivity is of |
| A. | Iron |
| B. | Lead |
| C. | Aluminium |
| D. | Rubber |
| Answer» E. | |
| 335. |
For better C.O.P of refrigerator, the pressure range corresponding to temperature in evaporator and condenser must be |
| A. | Small |
| B. | High |
| C. | Equal |
| D. | Anything |
| Answer» B. High | |
| 336. |
The wet bulb temperature during sensible heating of air |
| A. | Remains constant |
| B. | Increases |
| C. | Decreases |
| D. | None of these |
| Answer» C. Decreases | |
| 337. |
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 | |
| 338. |
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. | |
| 339. |
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 | |
| 340. |
A certain refrigerating system has a normal operating suction pressure of 10 kg/cm gauge and condensing pressure of about 67 kg/cm. The refrigerant used is |
| A. | Ammonia |
| B. | Carbon dioxide |
| C. | Freon |
| D. | Brine |
| Answer» C. Freon | |
| 341. |
Pick up the wrong statement. A refrigerant should have |
| A. | Tow specific heat of liquid |
| B. | High boiling point |
| C. | High latent heat of vaporisation |
| D. | Higher critical temperature |
| Answer» C. High latent heat of vaporisation | |
| 342. |
The sensible heat factor during the heating and humidification process is given by (where h‚ÇÅ = Enthalpy of air entering the heating coil, h‚ÇÇ = Enthalpy of air leaving the heating coil, and hA = Enthalpy of air at the end of humidification process)# |
| A. | (hA - h2)/ (h1 - h2) |
| B. | (h2 - hA)/ (h1 - h2) |
| C. | (h1 - h2)/ (hA - h2) |
| D. | (hA - h1)/ (h2 - h1) |
| Answer» E. | |
| 343. |
In which of the following refrigeration system, waste heat can be effectively used? |
| A. | Vapour compression cycle |
| B. | Vapour absorption cycle |
| C. | Air refrigeration cycle |
| D. | None of these |
| Answer» C. Air refrigeration cycle | |
| 344. |
The condition of refrigerant as it leaves the compressor in a vapour compression system is |
| A. | Saturated liquid |
| B. | Wet vapour |
| C. | Dry saturated vapour |
| D. | Superheated vapour |
| Answer» E. | |
| 345. |
The C.O.P. of a refrigeration cycle with lowering of condenser temperature, keeping the evaporator temperature constant, will |
| A. | Increase |
| B. | Decrease |
| C. | May increase or decrease depending on the type of refrigerant used |
| D. | Remain unaffected |
| Answer» B. Decrease | |
| 346. |
It is desired to condition the outside air from 70% relative humidity and 45° C dry bulb temperature to 50% relative humidity and 25° C dry bulb temperature (room condition). The practical arrangement will be# |
| A. | Dehumidification |
| B. | Cooling and humidification |
| C. | Cooling and dehumidification |
| D. | Dehumidification and pure sensible cooling |
| Answer» D. Dehumidification and pure sensible cooling | |
| 347. |
The refrigerant after condensation process is cooled below the saturation temperature before throttling. Such a process is called |
| A. | Sub-cooling or under-cooling |
| B. | Super-cooling |
| C. | Normal cooling |
| D. | None of these |
| Answer» B. Super-cooling | |
| 348. |
Condensing temperature in a refrigerator is the temperature |
| A. | Of cooling medium |
| B. | Of freezing zone |
| C. | Of evaporator |
| D. | At which refrigerant gas becomes liquid |
| Answer» E. | |
| 349. |
When the temperature of the surrounding is higher than the temperature of the body, then the heat loss by convection from the body to the surrounding will be |
| A. | Positive |
| B. | Negative |
| C. | Zero |
| D. | None of these |
| Answer» C. Zero | |
| 350. |
Most of the domestic refrigerators work on the following refrigeration system |
| A. | Vapour compression |
| B. | Vapour absorption |
| C. | Carnot cycle |
| D. | Electrolux refrigerator |
| Answer» B. Vapour absorption | |