photo credit: Paal Bentdal
The History of the Light Bulb
Here's what happens when a light bulb comes on and the filament is in air. Don't try this experiment at home unless you work with an adult (and even then be very careful).
The glowing filament rapidly heated the air around it, so the heated air expanded and formed the rising smoke column. But the rising gas cooled and became more dense, so it eventually stopped rising. Then the air at the top moved out to the side, forming the swirls in the photograph. To see the direction of flow within the rising air column, check out this drawing.
For an award-winning video showing how to make smoke rings and mushroom clouds, click here.
Login to Comment on this Item
Cardboard Tube Syllabus
What happens when each eye gets a different message? Try the activities in the Exploratorium's Cardboard Tube Syllabus to find out. For a related illusion--and a remarkable one--see Cheshire Cat.