3B Scientific Air Cushion Plate - Handbuch (Seite 95)

Physical Experiments on the Air-Cushion Table
44
Model simulation
Real Object Model
Part of a Experiment surface of
semiconductor the air-cushion table
Crystal lattice of Lattice model
the semiconductor
Positive ions of the
Lattice magnets
crystal lattice
Electrons
Hover discs
How to proceed:
Align the air-cushion table horizontally and at-
tach the magnetic barriers. Spread the discs
evenly across the experiment surface. Attach the
holding device to the air-cushion table and insert
the lattice model. Set it to a medium height.
Turn the fan to a setting in which all discs are
sure to lift off. If necessary, use the manipulating
rod to ensure that there is a disc under each hang-
ing magnet. Repeatedly open the impulse valve
to increase the velocity of the hover discs. Ob-
serve their configuration and motions.
Finally, gradually increase the degree of inclina-
tion of the table using the adjusting screw at bar-
rier no. 2 and observe the influence of the degree
of inclination on the hover discs.
Result:
At low velocities, all hover discs are positioned
under the magnets of the lattice model. At higher
velocities, some of the hover discs leave their
positions. The effect of inclining the experiment
surface is that the disordered motions of the hover
discs receive a preferential direction.
Interpretation:
In an intrinsic semiconductor, some electrons are
released from the lattice under the influence of a
rise in temperature, so that they move through-
out the semiconductor. The released electrons
leave behind positive “holes”. The number of
migrating electrons and the number of holes are
equal. Feeding voltage causes an electric cur-
rent to flow. The preferential motion of the elec-
trons is towards the positive electrode, that of the
“holes”, as it seems, in the opposite direction.
2.4.12 Electric Conduction in a
Semiconductor – N-Type Conduction
(Demonstrated By Means of
Mechanical Forces)
Components:
Air-cushion table with fan
Overhead projector
Magnetic barrier, long
2 Pieces
Magnetic barrier, short 2 Pieces
Holding device 1 Piece
Lattice model 1 Piece
Manipulating rod 1 Piece
Hover disc, red 28 Pieces
Model simulation
Real Object Model
Part of a semi- Experiment surface of
conductor the air-cushion table
Crystal lattice of Lattice model
the semiconductor
Positive ions of
Lattice magnets
the crystal lattice
Electrons
Hover discs
Strength of the Inclination of the
electric field experiment surface
How to proceed:
Align the air-cushion table horizontally and at-
tach the magnetic barriers around the experiment
surface. Spread the discs evenly across the ex-
periment surface. Attach the holding device and
insert the lattice model. Set it to a medium height.
Turn the fan to a setting in which all hover discs
float freely. Observe the configuration and mo-
tions of the hover discs. Then tilt the experiment
surface of the air-cushion table.
Open the impulse valve several times and repeat
the experiment at an increased velocity of the
hover discs.
Result:
At the lower velocity, 25 hover discs are bound
rather closely to the magnets of the lattice model.
The other three move in the gaps between them
in disorderly fashion. The effect of inclining the