Wind chill

March 12, 2001
Web posted at: 7:28 PM EST (0028 GMT)

Small-Scale Investigation: Wind Chill activity from Modern Earth Science, Holt, Rinehart and Winston, 1998, p. 510.

Wind chill is a term used by meteorologists to describe the relationship between temperature and wind speed. While values are usually read from a chart, wind chill is based on the physics of evaporative cooling. You can demonstrate the cooling power of moving air with a simple model.

Materials
shallow pan, about 23 x 33 cm
water
thermometer
electric fan
clock or watch with second hand
metric ruler

Procedure
1. Place the pan on a level table, and fill it to a depth of about 1 cm with water at room temperature.
2. Lay the thermometer in the center of the pan with the bulb submerged. Be sure you can read the temperature without touching the thermometer.
3. Do not disturb the pan for 5 minuters, then read and record the water temperature.
4. Position an electric fan a few centimeters from the pan, and face the fan toward the pan.
CAUTION: Do not get the fan or cord wet.
5. Turn on the fan at a low speed, and observe and record the water temperature every minute until the temperature remains constant.
6. If the fan has different speed settings, repeat Step 5 with the fan at a higher speed.

Analysis and Conclusions
1. How does the moving air affect the temperature of the water?
2. The moving air is the same termperature as the still air in the room. What causes the temperature to change?
3. On a cool, windy day, how would you dress to stay comfortable outdoors? Explain your answer.