Experiment of the Week - #131 Blowing Out a Candle?
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
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.