3B Scientific Air Cushion Plate - Handbuch (Seite 93)

Physical Experiments on the Air-Cushion Table
42
Model simulation
Real Object Model
Part of a metal Part of the experiment
surface under the
dynamic lattice
Vacuum Part of the experiment
surface not situated
under the dynamic
lattice
Metal lattice Lattice model
Electrons Hover discs
How to proceed:
Align the air-cushion table horizontally and ar-
range the magnetic barriers. Attach the holding
device and insert the lattice model. Set it to a
medium height. Slide it outwards in the groove
until 2 rows of the hanging magnets are located
above the impulse valve. Attach one red disc to
each hanging magnet of the remaining 3 rows.
These cling to the magnets due to the magnetic
attraction. Place the green discs on the experiment
surface and slide them under the lattice model.
Turn up the fan to a setting in which all discs are
sure to lift off. Briefly open the impulse valve
several times to increase the mean velocity of the
hover discs and the amplitude of the hanging
magnets. Observe the behavior of the hover discs.
Result:
Some of the hover discs overcome the forces of
the lattice magnets and return to the vacant area
of the air-cushion table. Some discs return to the
space underneath the lattice model. The stronger
the motions of the hover discs or lattice magnets,
the more hover discs escape the space under the
lattice model.
Interpretation:
To enable the electrons to escape the surface, they
have to possess a specific minimum energy. This
corresponds to the work of escape. Some of the
electrons possess this kinetic energy at high tem-
peratures of the metal. The higher this tempera-
ture is, the more electrons can escape it in a spe-
cific period of time.
2.4.9 Bound Charge Carriers in an
Insulator
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 25 Pieces
Model simulation
Real Object Model
Part of an insulator Experiment surface of
the air-cushion table
Crystal lattice of Lattice model
the insulator
Strength of the
Inclination of the
electric field experiment surface
Electrons Hover discs
How to proceed:
Align the air-cushion table horizontally and at-
tach the magnetic barriers. Spread the 25 hover
discs evenly across the experiment surface. Then
attach the holding device and insert the lattice
model. Set it to the lowest possible height, tak-
ing care, however, that the hover discs are not
attracted by the hanging magnets.
Turn the fan to a setting in which all hover discs
lift off. Observe their motions and interactions
with the lattice model. Then gradually increase
the degree of inclination of the experiment sur-
face and observe the behavior of the hover discs.
Result:
All hover discs are tightly bound to their loca-
tion and oscillate around their equilibrium posi-
tion at low amplitudes. Even when the experi-
ment surface is inclined to a higher degree, they
will not escape their positions.