Chapter U3, Problem 12RE

Interpretation Introduction

Interpretation :

Whether one feels cooler at 100 % relative humidity at 28°C or at 45 % relative humidity at 28°C must be explained.

Concept Introduction :

Lesser the relative humidity greater is the water evaporation rate.

Answer to Problem 12RE

One will feel cooler at 45 % relative humidity at 28°C as compared to 100 % relative humidity at 28°C.

Explanation of Solution

When the relative humidity is only 45 % air still has capacity to hold water vapor. So water is evaporated from our body as sweat. The latent heat of evaporation is taken from our body and it becomes cooler. But if relative humidity is 100 % then the air is saturated with water vapor and can’t hold more vapor at that temperature. So easily the sweat from our body will not be evaporated.

Conclusion

Thus, one will feel cooler at 45 % relative humidity at 28°C as compared to 100 % relative humidity at 28°C as rate of evaporation of sweat is possible in case of 45 % relative humidity.