Demos: 2C-02 Heron's Siphon


This demonstration makes use of the compressibility of air and the relative incompressibility of water. Water is poured into funnel, starting a process that continues until virtually all of the water is transferred.

Directions: Using a small beaker, pour water slowly into the funnel until water begins to drip from the upper tube. The process will now be self-sustaining. The water flowing into the lower can through the funnel, pushes air out of that can, through the tube and into the upper can. The increased air pressure pushes the water down in the upper can, and because of the incompressibility of the water, drives it up the upper tube, where it pours into the funnel, continuing the process.

Suggestions for Presentation: Just for fun, announce that you have a perpetual motion device, that once started, will continue to operate without outside interference. Start the system and let it run for a bit. Then ask the students if they can figure out what is happening.

Applications: None

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Last Updated: May 9, 2016 11:44 AM