Question

The purpose of rotating a whirling hygrometer in hygrometric survey is to

• A. Wet the cotton wick with water thoroughly
• B. Maintain constant temperature of water in the container
• C. Create steady state evaporation of moisture from the wet bulb surface
• D. Prevent the heat produced by the cap lamp of the observer from affecting the readings

Hint:

Proper rotation of a whirling hygrometer is essential for accurate humidity measurements, which are critical for maintaining safe working conditions in mines.

Answer 1

The Correct Option is C

A whirling hygrometer is used in hygrometric surveys to measure the relative humidity in a mine by comparing the temperatures of a wet bulb and a dry bulb. Rotating the hygrometer ensures that air flows consistently over the wet bulb, creating a steady state of evaporation from the wet bulb surface. This steady evaporation cools the wet bulb due to the latent heat of vaporization, allowing an accurate temperature difference to be measured between the wet and dry bulbs, which is then used to calculate humidity. The rotation does not primarily wet the wick, maintain water temperature, or prevent heat interference from a cap lamp.
Thus, the correct answer is Create steady state evaporation of moisture from the wet bulb surface.