''Bell jar model lung
demonstration''

This simple Bell jar model lung can be used to demonstrate the basic principles of breathing. The model should be assembled as in the diagram. A swimming cap makes a suitable diaphragm. The cap can be attached to the bottom of the bell jar, and the balloons can be attached to the Y shaped tube, with elastic bands or plastic coated wire.

How the Model Works

The cavity inside the bell jar is airtight.
  • As the diaphragm is pulled down, the volume of the cavity increases. This causes the pressure to fall. Air rushes in to equalise the pressure causing the balloons to inflate.
  • As the diaphragm is pushed up, the volume of the cavity decreases, the pressure rises, and the air rushes out of the ballons causing them to deflate.

See Also