Relevant Resource questions :

Concepts demonstrated :

• phase transformations
• evaporative cooling

• wet and dry bulb thermometer
• air gun

• Place water in the stand for the wet bulb and ensure that the material to the wet bulb is wet.

None

Physics involved :

The wet bulb thermometer is evaporitively cooled. This means that in order for the water to evaporate it must get its energy from somewhere. It does this by taking some of the energy from the thermometer.
The wet and dry bulb thermometer are used to measure relative humidity. Used in the Life Science fields.

How to use the Demonstration :

• POE - do students expect the temperatures to be the same?
• If the temperatures are not the same which thermometer do they expect to have the higher temperature?
• Place the thermometers in a warm area and measure the temperature.
• Measure the temperature when a breeze is blowing. The temperature should be lower for the wet bulb thermometer.
• Ask the class to explain why the wet bulb has a different temperature to the dry bulb.

• wind chill factor (especially in cold climates)

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