How can one determine the relative humidity on a particular day at a given place?

Evaporation from the surface of a given liquid takes place more rapidly when

The efficiency of a Carnot engine operating between two heat reservoirs at temperatures T1 and T2 (T1 > T2) is given by:

Which one of the following regarding density of water at atmospheric pressure is correct ?

Transfer of heat by convection can take place in

On a day when I am in hurry to go to office, I have a fixed quantity of rice which was just cooked and kept in a bowl. In order to cool it quickly, which one of the following is the best option?