Crookes' radiometer (Radiómetro de Crookes)

Topic: Physical Sciences Subtopic: Heat & Thermodynamics

Case Study

of an Exhibit

by Karina Ocana

Published on October 05, 2008

  • Description and goals

    Transforming light and heat into movement!

    This exhibit shows how a Crookes’ Radiometer works. The radiometer was invented and constructed by Sir William Crookes to measure the energy produced by light radiations. This device is a glass bulb with a tiny windmill inside and with a partial vacuum, that spins whenever it is exposed to infrared radiation. Its response is directly proportional to the amount of radiation received.

    As it can be seen in the pictures, it has 3 radiometers that are exposed to 3 light bulbs that emit different amounts of infrared radiation, since the first one is a fluorescent lamp, the second one is an incandescent light bulb and the third one is an infrared bulb. Actually, the three of them look almost the same, this was done in order to make the visitor much more curious about this phenomenon. Of course the tiny windmill wont spin at all with the fluorescent lamp, with the incandescent bulb will spin fast and finally with the infrared bulb will spin quite fast.

    This exhibit is the second version we have designed about this topic, since we think is very important to make clear for our visitors how this radiometer works. Our objective is to show and explain in a very concrete way how the tiny windmill spins due to the air current that is generated inside the glass bulb, when the small amount of air is heated by the infrared radiation produced by the lamps.

    This exhibit is part of a set of 10, that we at the Centro de Difusión de Ciencia y Tecnología, designed, developed and built for the Museum “El Rehilete”, a children’s museum located in Pachuca, Hidalgo Mexico.

  • Exhibit Opened: 2006

  • Location: Pachuca, Hidalgo, Mexico

Latest Comments (2)

Drawer slides

by Michael Flynn - October 10, 2008

That is a nice touch to have the electronic board mounted on an easily accessible roll-out tray. What do the electronics do in this exhibit?

About the electronics

by Karina Ocana - October 10, 2008

The electronic circuit controls the amount of time that the lamps are turned on to see the phenomenon, and the minimum time they have to be turned off, so the radiometer’s windmill can stop spinning. And be ready to make them spin again.

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