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Code Number: 7D30.45
Demo Title: Smoke Detector
Condition: Excellent
Principle: Particle Decay and Ionization
Area of Study: Modern Physics
Equipment:
Smoke Detector, Radiation Counter if Desired, Amplifier and Speaker.
Procedure:
Open up the smoke detector and pass it around and show that the active element is composed of Americium 241. The Geiger counter may be used to detect the radiation coming off of the source. These are alphas so they won't travel a great distance.
A point of interest is that Americium 241 has a half-life of 432.2 years. So, as long as you put batteries in your smoke detector regularly, it should last for several lifetimes.
References:
- Lawrence Ruby and John Hunt, "Understanding Modern Electrical Protective Devices", TPT, Vol. 35, #7, Oct. 1997, p. 432.
- Jack G. Gouch and Kelly L. Vaughn, "Radioactive Consumer Products in the Classroom", TPT, Vol. 33, #1, Jan. 1995, p. 18.
- H. Richard Crane, "Ionization Smoke Alarms", TPT, Vol. 22, #8, Nov. 1984, p. 526 - 528.
- J. R. Young, "The Smoke Detector", TPT, Vol. 17, #7, Oct. 1979, p. 467.
- Curt Suplee, "Inner sanctum", Everyday Science Explained, National Geographic, p. 126.
- Borislaw Bilash II, “Actinide Elements are Useful“, A Demo A Day – A Year of Physical Science Demonstrations, p. 139.