Mrs. Deringer's Relative Humidity Web Page

Relative Humidity:

Humidity is the measure of the amount of water vapor in the air. The percentage of water vapor in the air compared to the maximum amount the air can hold is called the relative humidity.

As you can see warmer air can hold more water vapor.

Relative humidity can be measured using a psychrometer. It has two thermometers, a wet-bulb thermometer and a dry-bulb thermometer. The bulb of the wet-bulb thermometer has a cloth covering that is moistened with water.

Air is then blown over both thermometers. Because the wet-bulb thermometer is cooled by evaporation, its reading drops below that of the dry-bulb thermometer.

 

On the other hand, if the relative humidity is high, the water on the wet-bulb will evaporate slowly and the wet-bulb temperature will not change much.
You will be using a relative humidity chart to record the percentage of the relative humidity. When the relative humidity is high there is a greater chance for precipitation. When the relative humidity is low there is a lower chance for precipitation.

 

Directions on how to use the Relative Humidity chart:

When given wet and dry bulb readings.

Dry bulb= 28 degrees

Wet bulb = 14 degrees

1. Subtract the wet bulb reading from the dry bulb reading. 28 - 14 = 14 (difference)

2. Use the chart by locating the dry bulb reading (28)on the left hand side of the chart and lining that up with tthe difference (14) on the top of the chart. Therfore the relative humidity is 17%. Little chance of precipitation.

When the relative humidity reaches 100% then it will rain, snow, sleet or hail.

Watch how a Football trainer uses a sling pshchrometer to protect his players from the intense heat.

Learn ways to protect yourself when you are playing sports in the heat.

 

RELATIVE HUMIDITY PRACTICE QUESTIONS

1. If on Monday the dry bulb is 14 degrees and the wet bulb is 10 degrees the realtive humidity is

2. If on Tuesday the dry bulb is 16 degrees and the wet bulb is 16 degrees the realtive humidity is

3. If on Wednesday the dry bulb is 28 degrees and the wet bulb is 20 degrees the realtive humidity is

4. If on Thursday the dry bulb is 16 degrees and the wet bulb is 6 degrees the realtive humidity is

5. Which day would have the greatest chance for precipitation?

6. What happens when the relative humidity is 100%

7. If there is a big difference in the dry bulb reading and the wet bulb reading then you know that there is for precipitation because a lot of the water was able to evaporate.

8. If there is a SMALL difference in the dry bulb reading and the wet bulb reading then you know that there is for precipitation because the air is saturated and NOT a lot of the water was able to evaporate.

9. If there is NO difference in the dry bulb reading and the wet bulb reading then you know that the air is saturated and it will

10. The closer the Relative humidiy is to 100% the

 

 

 

 

 

 


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