3B Scientific Air Cushion Plate - Handbuch (Seite 96)

45
Physical Experiments on the Air-Cushion Table
experiment surface is that the disordered motions
of the hover discs are superimposed by directional
movements. An increase in velocity also causes
some of the bound discs to leave their positions.
Interpretation:
In a semiconductor with N-type conduction, mi-
grating electrons are found even at low tempera-
tures. Feeding voltage causes a current to flow,
this current being produced by these electrons.
At higher temperatures, further electrons are re-
leased for the charge transport.
2.4.13 Electric Conduction in a
Semiconductor – P-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 22 Pieces
Model simulation
Real Object Model
Part of a semi- Experiment surface of
conductor the air-cushion table
Crystal lattice of the Lattice model
semiconductor
Positive ions of the
Lattice magnets
semiconductor
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. Spread the 22 discs
evenly across the experiment surface, attach the
holding device and insert the lattice model. Set it
to a medium height.
Turn the fan to a setting in which the discs are
sure to lift off. Then tilt the experiment surface.
Observe the configuration and motions of the
hover discs. Repeat the experiment at an increased
velocity of the hover discs.
Result:
The hover discs are bound to the magnets of the
lattice model. Some positions, however, remain
vacant. As adjacent discs change over into va-
cant positions, the “holes” move. The inclination
of the experiment surface causes a superimposi-
tion of a directional movement.
Interpretation:
In a semiconductor with p-type conduction some
locations within the lattice are not occupied by
electrons. These “holes” are often filled up by
adjacent electrons, creating new “holes.” When
feeding a voltage, the positive “holes” move in
the direction of the negative electrode. At higher
temperatures, additional “holes” are created.