Lakshya Education MCQs

Question: 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)
Options:
A. 25 kJ/kg
B. 50 kJ/kg
C. 100 kJ/kg
D. 125 kJ/kg
Answer: Option B
Explanation :

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Question 1. The relative humidity is defined as
  1.     The mass of water vapour present in 1 m3 of dry air
  2.     The mass of water vapour present in 1 kg of dry air
  3.     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
  4.     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: Option D
Explanation :
Question 2. The relative humidity is defined as
  1.     The mass of water vapour present in 1 m3 of dry air
  2.     The mass of water vapour present in 1 kg of dry air
  3.     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
  4.     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: Option D
Explanation :
Question 3. The dry bulb temperature during sensible heating of air
  1.     Remains constant
  2.     Increases
  3.     Decreases
  4.     None of these
Answer: Option B
Explanation :
Question 4. Moisture in freon refrigeration system causes
  1.     Ineffective refrigeration
  2.     High power consumption
  3.     Freezing automatic regulating valve
  4.     Corrosion of whole system
Answer: Option C
Explanation :
Question 5. The wet bulb temperature during sensible cooling of air
  1.     Remains constant
  2.     Increases
  3.     Decreases
  4.     None of these
Answer: Option C
Explanation :
Question 6. The dry bulb temperature during sensible heating of air
  1.     Remains constant
  2.     Increases
  3.     Decreases
  4.     None of these
Answer: Option B
Explanation :

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