3B Scientific Air Cushion Plate - Manual (Page 30)

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Physical Experiments on the Air-Cushion Table
2.2.4 Brownian Motion in a Liquid
Components:
Air-cushion table with fan
Overhead projector
Magnetic barrier, long
2 Pieces
Magnetic barrier, short 2 Pieces
Hover disc, orange 25 Pieces
Hover disc, blue l Piece
Model simulation
Real Object Model
Vessel containing Experiment surface of
the liquid the air-cushion table
Walls of the vessel Magnetic barriers
Molecules of Orange hover discs
the liquid
Particle showing the Blue hover disc
Brownian motion
How to proceed:
Align the air-cushion table horizontally and attach
the magnetic barriers.
Arrange the orange discs near the magnetic
barriers of the air-cushion table. Place the blue
disc at the center of the experiment surface.
While the impulse valve is opened, turn up the
fan so that all hover discs lift off. Then briefly
open the impulse valve every now and then.
Observe the motion of the blue disc interacting
with the orange ones.
Result:
Repeated impacts of the orange discs cause a
disordered motion of the blue disc. Its mean ve-
locity over time is much lower than the mean
velocity of the orange discs.
Interpretation:
If a liquid contains microscopically small par-
ticles the thermal motion of the invisible mole-
cules sets them into an irregular motion which
can be observed under the microscope.
2.2.5 Evaporation of a Liquid
Components:
Air-cushion table with fan
Overhead projector
Magnetic barrier, long
2 Pieces
Magnetic barrier, short 2 Pieces
Holding device 1 Piece
Plexiglas plate 1 Piece
Flat magnetic barrier 1 Piece
Hover disc, green 10 Pieces
Model simulation
Real Object Model
Vessel containing Experiment surface of
the liquid the air-cushion table
Walls of the vessel Magnetic barriers
Surface of the liquid Flat magnetic barrier
Molecules of
Hover discs
the liquid
How to proceed:
Align the air-cushion table horizontally and attach
the magnetic barriers. Then tilt the experiment
surface by screwing in the adjustment screw on
barrier no. 4. Arrange the hover discs on the half
of the experiment surface adjacent to barrier no.
3. Fasten the holding device to the air-cushion
table and insert the Plexiglas plate. Place the flat
magnetic barrier onto the Plexiglas plate so that
it runs parallel to the magnetic barriers nos. 3
and 4, below the center. The magnetic strip should
face down, with the arrow pointing to the
projecting wall. Then set the plate to the lowest
position.
Turn the fan to a medium setting. Observe the
behavior of the hover discs, especially those near
the flat magnetic barrier. Then gradually increase
the mean velocity of the hover discs by briefly
opening the impulse valve several times.
Result:
The slow hover discs cannot exit the lower part
of the experiment surface. The faster ones, how-
ever, cross this border and reach the upper section
of the experiment surface. Here they move in a
straight and uniform way until hitting other hover
discs or the magnetic barrier. Occasionally, discs
will also return to their original space.