Pressure

Principles Illustrated: Atmospheric force, Pressure differentials

Location: Cabinet D, Shelf 3

A classic demonstration of pressure differentials. A rectangular 'gas can' contains a cup or so of water. The can is placed on a hot plate until the water boils. The can is then capped and placed on its side in an ice water bath. The resulting pressure differential between the cooling water vapor inside the can and atmospheric pressure outside the can causes the can to collapse dramatically.

Alternatively, the demonstration can be done with a soda can. The steam filled can is turned upside-down in a water bath. The collapse is startling and dramatic. When the can is removed from the bath, it is nearly full of the water due to the vacuum created by the condensation of the steam.

Principles Illustrated: Self-leveling of fluids

Location: Cabinet D, Shelf 2

Tubes of various sizes and shapes are connected to a common reservoir at their bottoms. The level of the fluid in each tube is the same as the others.

Principles Illustrated: Force of pressure differentials

Location: Cabinet D, Shelf 4

Otto von Guericke, Mayor of Magdeburg, Inventor of vacuum pump

In 1654, in a famous series of experiments that were performed before Emperor Ferdinand III at Regensburg, Guericke placed two copper bowls (Magdeburg hemispheres) together to form a hollow sphere about 35.5 cm (14 inches) in diameter. After he had removed the air from the sphere, horses were unable to pull the bowls apart, even though they were held together only by the air around them. Thus the tremendous force that air pressure exerts was first demonstrated.

Our 5 inch sphere is vacuumed out using a hand-pump and then sealed with a stopcock.