Experience this sphere powered by the sun!
A Crookes' radiometer has four vanes suspended inside a glass bulb. Inside the bulb, there is a good vacuum. When you shine a light on the vanes in the radiometer, they spin -- in bright sunlight, they can spin at several hundred rotations per minute! No batteries required.
The vacuum is important to the radiometer's success. If there is no vacuum (that is, if the bulb is full of air), the vanes do not spin because there is too much drag. If there is a near-perfect vacuum, the vanes do not spin unless they are held in a friction-less way. If the vanes have a friction-less support and the vacuum is complete, then photons bouncing off the silver side of the vanes push the vanes, causing them to rotate. However, this force is exceedingly small.
If there is a good but incomplete vacuum, then a different effect called thermal transpiration occurs along the edges of the vanes, as described on this page. The effect looks as though the light is pushing against the black faces. The black side of the vane moves away from the light. This is the case with this radiometer.
*Prices subject to change without notice. We reserve the right to limit quantities.
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Part No
01800
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Manufacturer
TEDCO
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Stock No
3555-GF1
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SKU No
215975
To purchase bulk quantities, Please contact our Sales Department
(+1-416-494-8999) or email shop@sayal.com
