by: Bruce Yeany

The principle of a lightbulb can be demonstrated without the danger of creating a vacuum inside a glass jar. One of the difficulties in demonstrating a lightbulb centers on the removal of air from the chamber using a vacuum pump. The device in this chapter suggests two alternative methods. The first uses several lit candles inside a jar to burn up as much of the available oxygen as possible before turning on the power. The second is to release helium into the jar. This lighter-than-air gas will push most of the air out of the bottom of the container. The mechanical pencil "lead" filaments may last up to 2 minutes before burning out with these methods.


Middle SchoolHigh School


Type Book ChapterPub Date 1/1/2006

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