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GATE 2017 ME (ME2) – Question 25

Thermal Engineering Applications · Psychrometry and air-conditioning · 1 mark · Multiple choice

Moist air in a closed metallic vessel is heated. Its ______.

  1. relative humidity decreases
  2. relative humidity increases
  3. specific humidity increases
  4. specific humidity decreases

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Show answer and explanation

Correct answer: (A) relative humidity decreases

Explanation

No water vapour or dry air enters or leaves, so humidity ratio remains constant in the absence of condensation. Heating increases saturation vapour pressure faster than the actual vapour pressure, reducing their ratio. Thus **relative humidity decreases, A**; specific humidity does not increase.