Question

when you blow air out ,through which boiling tube does the air flow out of the apparatus? can you say why the air does not go out through the other boiling tube as well?​

Answer 1

Answer:

Very interesting observation. I think what you are observing when your mouth is away from the tube is MORE than just the air you exhale - because the air in the vicinity of your breath is being "dragged along" by something called "entrainment". This is the principle behind an ingenious fan, called the Dyson Air Multiplier: