As a rule, the relative air humidity measured as a percentage has practical value. It shows the attitude of water vapor in air to their greatest possible quantity at this temperature. For determination of humidity the devices which are called psychrometers are used.
It is required to you
- Two mercury thermometers, cotton wool, water
Instruction
1. The principle of operation of the simplest psychrometer rather just allows to define humidity of air without special devices. Take the ordinary mercury thermometer, track that it was dry, and take air temperature. Then take a little cotton wool, wet it in water and wind a tip a thermomeasure. The value of the thermometer will begin to fall because from the surface of cotton wool water will evaporate and to select heat at the thermometer. When falling stops, take readings of the thermometer once again. The difference between indications of the dry and damp thermometer depends on that how many vapors in air already are, in other words from humidity. The humidity is less, the this difference will be higher. Values of a difference for different temperatures of the dry thermometer are available in the special psikhrometrichesky table, it can easily be found in the Internet. Determine values of humidity by it.
2. If the value of humidity is required to be known constantly, it is simple to produce by a similar method own simplest psychrometer and to determine humidity of air by it at any time. Take two thermometers and fix them next to each other. Under one of them place a bath with water in which place vatu so that it became wet and constantly concerned a thermometer tip. Two thermometers will show different values, by means of the table you determine value of relative air humidity by a difference of indications.