Home Science Experiment: A Dancing Flame

Controlling a Flame

What is needed: a candle; a funnel.

Light the candle. Hold the funnel near the candle, its mouth facing the candle and its narrow end facing you (as seen in the photo), and blow fiercely into the funnel. Does the flame die out?

... Hint: the explanation has to do with the difference of air pressures inside the funnel and around it. You can easily understand what "air pressure" is if you try squeezing an inflated balloon (or imagine you do so): the balloon "resists", i.e., it generates counter-force. This force is called "air pressure". When blowing into the funnel, the air pressure inside it is lower than that around it. This causes air from around the funnel to flow into it, thus "bending" the flame toward the funnel.