Hot Air Currents

Purpose: To learn about convection air currents

Materials

• white paper
• scissors
• pencil
• large sewing needle
• sewing thread or string
• lightbulb in lamp

Procedure

1. Print out this activity sheet or trace the pattern illustrated below on a piece of white paper.
2. Cut out the spiral pattern.
3. Thread a large needle with the sewing thread (string). Bring the ends of the sewing thread or string together and make a knot.
4. Poke the large needle through the circle at the top of the spiral and pull the thread through so the spiral pattern hangs easily by the thread (string).
5. Hold the cutout spiral above an electric lightbulb. Don't place the paper on top of the bulb!
6. Turn on the lightbulb and make observations.

Conclusion

1. What happened as the spiral hung over the lightbulb? Record your response in your science journal.
2. Does the distance between the spiral and the lightbulb affect what happens?

What's Happening?
The air around the electric lightbulb is heated, which causes the air molecules to expand and move around. As the air is heated, it becomes less dense and rises while the cold air sinks. The rising air molecules (hot-air currents) generated by the electric lightbulb cause the spiral to spin. This process is an example of convection in a gas (air).

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Answer Key

1. What happened as the spiral hung over the lightbulb?

The spiral pattern began to spin as the molecules in the air became heated and moved upward out of the way. The cooler molecules in the air then moved in and took their place. The process repeats itself, causing a constant upward flow of air as the air rises and is replaced by the cooler air.

2. Does the distance between the spiral and the lightbulb affect what happens?

The speed of the spiral's movement is directly related to the distance the spiral and the lightbulb are apart from one another. The closer to the bulb the spiral gets the greater the heat and the faster the spiral spins due to the rising air.