PURPOSE: To aid in illustrating how a siphon works.

DESCRIPTION: A bead chain passes over a pulley between two beakers. When one of the beakers is raised, the chain flows from the higher into the lower beaker, just as water flows from the higher to the lower container of a siphon. This is due the greater weight of the chain, or water, on the side of the lower container. Note that the cause of the siphon flow is not air pressure, which is greater at the surface of the lower container!

Click on the photograph at the right to see an mpeg video of the action.

SUGGESTIONS: Ask your students if a mercury siphon would work on the moon, in the absence of an atmosphere.

See Question of the Week #156 for information on using this demonstration to enhance class involvement.

REFERENCES: (PIRA 2B60.29)

EQUIPMENT: Siphon chain model, as photographed.

SETUP TIME: None.