The siphon

• In a siphon pressure is greatest in the lower end of the pipe
• The pressure will cause the liquid to flow out
• This reduces the pressure in the tube
• More liquid is forced into the tube by atmospheric pressure
• The siphon can be investigated using the following experiment

Experiment

Materials tin of water, 1m length of rubber tubing

Method

Siphoning a liquid

1. Place one end of the rubber tube into the tine of water
2. Suck the other end of the tube until the tube is full of water
3. Place your thumb over the tube and lower this end to a level below that of the water in the tin
4. Remove your thumb from the other end

Observations and Results

• Water starts to flow and the tin is emptied
• Water stops flowing if the water in the tin falls below the pipe
• Water will also stop flowing if the outer end of the tube is raised above the water in the tin

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