Physics | dewpoint what it is





Many of us have heard about the relative humidity and dew point (condensation temperature). Let’s look at what kind of values ​​and that they characterize. Air always contains a certain amount of moisture. But humidity depends not only on the contained water , but also on the temperature. Imagine that in the air “solution” a glass of water, provided that the room temperature 15.5 degrees Celsius.

Туман в лесу

University of Wisconsin in Madison has an interesting collection of physical experiments that can be performed at home. Materials in this collection will provide ideas for anyone who is interested in science.

If the room becomes colder air in the room and can not hold itself on this volume of water. Will fog formation and some of the water condenses on the walls. All we could see snow at times in the bathroom when they include hot water in the shower or sink. The temperature at which condensation or fog is formed is called the dew point (dew point). You yourself can determine the temperature of condensation in a simple physical experiment.
Equipment and materials

Large metal mug or pan
Thermometer for water, allowing to measure the temperature below zero (Celsius)
Experiment Progress

1. Fill the pan with water at room temperature.

2. Place the thermometer in the water and measure its temperature.

3. Leave the thermometer in the water and gradually enter into the water crushed ice. Do this gradually to observe the change in temperature, the thermometer.

4. At some point, the water starts to condense on the outside of the pan. The temperature at which this occurs will be dew point.

Конденсат на стенках душа

5. Try it in the bathroom after a shower. Or in a well-heated room. You will find that the dew point under different conditions will be different. In the dry winter day dewpoint can descend below the freezing point of water. In these circumstances, we considered the method of determining the temperature of condensation will not work because you can not cool the liquid water to a temperature below its freezing point, ie the transition to the solid state. A warm moist bathroom this method will work as before.


Relative humidity is directly related to the dew point. Relative humidity tells us about how the air is saturated with water and close to what is to stop it hold (to 100% relative humidity). Do not forget, upon the occurrence of the dew point temperature of the air decreases. To calculate the relative humidity, you need to know the condensing temperature and the air temperature.

At the same time learn how to translate the temperature in Fahrenheit to Celsius and vice versa. It is clear that in the modern world this task can be assigned to variables calculator , but it is desirable to know some things just for the overall development. The formula gives an approximate result.

C (the temperature in degrees Celsius) = (F + 40) * 0,556 (or rather five ninths) – 40

So, we need to know what temperature in Celsius correspond to 60 degrees Fahrenheit. We add 60 to 40, the result is 100. Multiply 100 by 0,556. The result is 55.6. From this number, subtract 40 and we know that 60 degrees Fahrenheit correspond approximately 15.6 degrees Celsius.

If the window is 20 degrees Celsius, and we would like to know how it Fahrenheit, then resort to another formula:

F (temperature in Fahrenheit) = (C + 40) * 1.8 (nine fifths) – 40

F = (20 + 40) * 1.8 – 40 * 1.8 = 60 – 40 = 108 – 40 = 68

20 degrees Celsius – it is 68 degrees Fahrenheit.

Calculations are performed in the same manner as in the previous example. First – the action in parentheses, and then – multiplication, and only in the last instance – subtraction. As taught in school mathematics lessons.

Приложение Dew Point для Android определение точки росы

Knowing the relative humidity and air temperature, Android users will be able to calculate the dew point using a very simple application Dew Point .

From the two sliders, allows it to exhibit a relative humidity (0% to 100%) and air temperature (not more than 50 degrees above zero Celsius). Yellow symbols on the left below shows the condensing temperature (dew point). And the bottom right light blue text displays absolute humidity indicator, how many grams of water (H2O) under specified conditions contained in a cubic meter of air.

Dew Point application is free. Its developer Markus Hoffmann posted in Google Play the latest version of Dew Point 1.05-13 December 27, 2013. The size of the APK-file is 45 kilobytes. Number of settings: from 10 thousand to 50 thousand. Dew point calculator Dew Point is compatible with Android 2.1 and later versions of the dominant mobile operating system.

Do you think it necessary to be able to nowadays in mind recalculate Fahrenheit to Celsius? Or the emergence of specialized calculators that knowledge was anyone (except physics) does not fit?
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