Things you need
Lighted, candle, Funnel
What to do:
Light a candle and blow hard through a funnel whose mouth is held a little away from the flame. You will find that you cannot blow out the candle. On the contrary the flame bends towards the funnel
Why?
Blowing through the funnel reduces the air pressure inside it. The air from outside rushes into the funnel, causing the flame to bend towards the funnel in the process. The air sweeps along the inside of the walls so if the edge of the funnel is held close to the flame it will be blown out
If you turn the spout of the funnel towards the candle and blow from the other end, that is, the mouth, the flame will be extinguished. In this case the air is compressed in the narrow spout, and blows out the flame as it exits.
Picture Credit : Google
