Question

What does the principle of the wet-bulb and dry-bulb thermometers state?

Answer 1

i think it's about how evaporation causes cooling but not sure.

Answer 2

Well, first off the wet bulb and dry bulb thermometer is for measuring the humidity in the air. This happens when one of the bulbs are wetted down and one left dry. After the water has evaporated and cooled the temperture of the bulb that was wetted down then you measure the difference between the two to get the humidity. The principle states that evaporation cools.