How The Drinking Bird Works
The drinking bird, also known at the happy drinking bird, the dippy bird or the nodding bird, is a classic physics toy used to demonstrate a range of scientific principles, or just as a great desktop toy.
The drinking bird, when its beak is dipped in a beaker of water placed in front of it, will begin 'drinking' steadily. The bird will slowly tip forward, until the beak dips into water. It will then tip upright and then slowly begin to tip again. The 'drinking' motion will continue as long as there is a constant supply of water.
The drinking bird has been created in a number of different designs, but all have the same basic features. The drinking bird itself is made of two glass bulbs, one with an extruded 'beak', joined by a tube.
This glass structure is balanced via arms attached to the tubes on a stand, allowing the bird to pivot.
The bird contains a volatile liquid such as ethanol, which is coloured to make it easier to observe the movement of liquid within.
How does the Drinking Bird work?
- You wet the drinking bird's head
- Water evaporates from the outside of the drinking bird's head
- This cools the drinking bird's head
- Which causes the vapour inside the drinking birds' head to condense
- This results in a lower pressure in the drinking bird's head
- Which sucks liquid up from the base of the drinking bird
- As liquid flows into the head, the drinking bird becomes top-heavy and tips forward
- When it tips over, the bottom end of the neck tube rises above the liquid in the bottom
- This causes vapour to rise up the tube to the head
- Which pushes liquid back down from the head to the bottom
- The increased weight of liquid in the bottom restores the drinking bird to an upright position
What physics does the Drinking Bird demonstrate?
This one experiment manages to demonstrate a whole range of physical laws, including the combined gas law, the ideal gas law, the Maxwell-Boltzmann distribution, the heat of vaporisation, torque, centre of mass and capillary action.