3B Scientific Air Cushion Plate - Handbuch (Seite 90)

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Physical Experiments on the Air-Cushion Table
Model simulation
Real Object Model
Space containing an Experiment surface of
electric field
the air-cushion table
Electrodes Electrodes
Charge carriers Aluminum hover discs
How to proceed:
Align the air-cushion table horizontally. Arrange
the two electrodes on two sides opposite each
other, so that they rest directly on the experiment
surface with their bases pointing upwards. Con-
nect them to the high-voltage source. Place a
hover disc directly next to an electrode.
Feed d.c. voltage to the electrodes. Turn the fan
to a setting in which the hover disc is sure to lift
off. Then place the remaining discs onto the ex-
periment surface one after the other, using the
tweezers and placing them directly next to an elec-
trode. Observe the motions of the hover discs.
Result:
The hover discs move back and forth between
the electrodes under the influence of the electric
field.
Interpretation:
When slightly moving particles (charge carriers)
are located in an electric field, they will pick up
charges at one electrode and transport them to
the opposing one. There they will discharge these
and pick up charges of the opposite polarity. Then
they will return to the first electrode, etc. This
directed movement of the charge carriers repre-
sents a current.
Notes:
This experiment offers a clear demonstration of
the conditions existing for example when grains
or aluminum flakes move back and forth between
the plates of a plate capacitor through the influ-
ence of the electric field.
This setup is also suited to simulate the process
of conduction with bipolar charge carriers. To do
this, place an approx. 8-cm wide cardboard strip
on each electrode. It should protrude from the
electrodes approx. 3 cm into the space between
the electrodes. When repeating the experiment
under these conditions, the charge carrier seems
to disappear in the respective electrode. Later it
will leave the electrode as a “different” charge
carrier (of the opposite polarity).
2.4.5 Influence of Lattice Elements on the
Motions of Electrons in an Electric Field
Components:
Air-cushion table with fan
Overhead projector
Holding device
Plexiglas plate
Electrode
2 Pieces
Manipulating rod 1 Piece
Hover disc, orange 1 Piece
Hover disc made of aluminum 4 Pieces
High-voltage source
Model simulation
Real Object Model
Part of a metallic Experiment surface of
conductor the air-cushion table
Lattice element Orange disc
of the metal
Electrodes
Electrodes
Conduction electrons Aluminum hover discs
How to proceed:
Align the air-cushion table horizontally. Arrange
the two electrodes on two opposing sides of the
experiment surface, so that they rest directly on
its surface with their bases pointing upwards.
Attach the holding device to the air-cushion table
and insert the Plexiglas plate. Place the four alu-
minum discs on the experiment surface and shift
them towards one of the electrodes. Connect the
electrodes to the high-voltage source.
Feed d.c. voltage to the electrodes. Turn up the
fan so that all hover discs lift off. Observe their