First, Hurricane Dennis has passed us without any damage or bad
weather. We did get a some pretty big waves, which the local surfers
loved, but that was about it. One of the hazards of living at the
beach is having to watch every tropical storm to see if it is coming
your way.
For this week's experiment, I wanted something that related to
hurricanes. I settled for one that is based on fast moving air and
differences in air pressure. You will need:
* a candle
* a funnel
* a mirror
Warning: This experiment uses fire. Be sure to get permission from an
adult and BE SAFE.
Place the candle into a holder or make a holder by crumpling some
aluminum foil around the base. Light the candle. Place the small end
of the funnel to your mouth. You are going to blow through the funnel
and try to blow out the candle. Easy, right? Try it and see what
happens. Unless you have a clear funnel, do this in front of a mirror
so you can see what is happening.
Not what you expected, was it? Instead of blowing the candle out, the
candle flame is pulled towards the funnel! The harder you blow, the
more the flame is pulled towards the funnel, but it does not blow
out, unless you know the secret. This secret will also help explain
what is happening.
Instead of pointing the center of the funnel towards the flame, point
the lower edge of the funnel towards it. This time, you will quickly
blow out the candle. Instead of flowing straight through the funnel,
the air is flowing along the sides of the funnel.
The fast moving air flows through the tube of the funnel until it
reaches the point where the funnel starts to spread. As we have seen
in past experiments, fast moving air exerts less air pressure than
slow moving air. The fast, low pressure air is forced to the sides,
flowing around the slow moving, high pressure air in the center of
the funnel. Some of this slow air is pulled along with the fast
moving air, creating a suction that pulls the flame towards the funnel.
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to Krampf Index Including permission to post
these
experiments on my web site.
