3B SCIENTIFIC PHYSICS U14350 Instructions D'utilisation page 2

3B SCIENTIFIC® PHYSICS
Operating instructions
1/03 ALF
The Pythagorean beaker allows an entertaining dem-
onstration of the principle of a siphon.
1. Safety instructions
• Handle the beaker carefully to avoid breakage.
• As the beaker is emptied almost fully during the
demonstration, measures to collect the liquid must
be taken beforehand.
2. Description, technical data
Although Pythagoras is famous mainly for his a² + b² = c²
(theorem for right-angled triangles), this is just one of
a series of accomplishments by the great thinker who
also delved into areas such as religion, the nature of
the soul and cosmic harmony. To demonstrate the vir-
tues of moderation to his students, he designed a bea-
ker named later after him. If the beaker is filled up to
a certain level with wine or water, for example, it re-
tains the liquid. However, adding any more liquid be-
yond this level causes the entire contents of the bea-
ker to drain out via a hole at the bottom. The beaker is
made of hand-blown glass, and the secret of its design
is a siphon installed in the middle of the beaker.
Height: 250 mm
Beaker diameter : 80 mm
3. Principle
The siphon in the middle of the beaker consists of a
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U14350 Pythagorean beaker
bent glass tube with a short arm extending from just
above the bottom of the beaker to the elbow, and a
long arm extending from this elbow to the outlet at
the foot of the beaker. The liquid columns in both arms
are governed by the laws of gravity, the long column
pulling the short one after it once an overflow occurs.
The liquid columns stay joined due to the external air
pressure which prevents the formation of a vacuum.
The water continues to flow out as long as the level of
the liquid in the vessel is higher than the opening of
the siphon's long arm.
S
1
Figure 1
Principle of how a siphon works
The flow of liquid is controlled by the water column S
level of the liquid, column S
4. Procedure
• Fill the beaker with liquid to a point just short of
the elbow.
• The beaker retains the liquid.
• Add more liquid until its level has risen beyond the
elbow.
• The beaker is drained almost fully as a result.
2
S
2
S
3
beneath the
3
being compensated by S .
2 1
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