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Earth Science Demo

Light Bulb Air Current And Wind

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From 101 Effective Earth Science Demonstrations Using Only One or Two Items, by William Johnston, with Mark Francek

Source: E. Richard Churchill, Louis V. Loeschnig, Muriel Mandell, and Frances Zweifel: 365 Simple Science Experiments with Everyday Materials (1997), page 220.

Objective: To learn about air currents and wind and how they relate to each other.

Standards: Structure of the Earth System (atmospheric composition and properties at different elevations; global circulation patterns and influence on local weather), Energy in the Earth System (heating of earths surface and atmosphere drives weather), and Properties and Changes in Matter (substance density).


About the Authors

Bill Johnston is a science teacher in southeastern Michigan. Mark Francek is an earth science educator at Central Michigan University.

Materials: talcum powder and unshaded lamp

Procedure:

  1. While the lamp is turned off and cool, sprinkle some talcum powder above it.
  2. Observe what happens.
  3. Light the lamp and let it warm up for a few minutes.
  4. When the lamp becomes hot, sprinkle more talcum powder above it. (You might want to turn off the light to see the full effect).
  5. Observe what happens.
You might want to practice this demo at home before presenting it in front of the class.

Science Behind It: When the lamp is heated, the powder rises up from the lamp because the bulb is producing heat and causing the air above it to rise and carry the powder with it. This represents convection, where the warmer air pushes upward because it is less dense and the molecules in the air are farther apart from one another. Before the lamp was hot, the talcum powder sank down along with the colder and denser air around the lamp. As the warm air rises, the cooler air flows in and sinks to occupy its place. Vertical movement of air is known as an air current, while horizontal movement of air on the same level is known as wind. The speed of air currents and wind is typically determined by the temperature difference between adjacent regions. The winds direction also depends on the location of those regions or areas.