3B Scientific Air Cushion Plate - Handbuch (Seite 73)

Physical Experiments on the Air-Cushion Table
22
velocity of the molecules and the number of im-
pacts. The temperature and pressure of the gas
increase. When expanding a gas adiabatically,
the mean velocity of the molecules decreases and
there is a drop in pressure and temperature.
2.1.12 Dependence of the Pressure on the
Temperature
Components:
Air-cushion table with fan
Overhead projector
Magnetic barrier, long
2 Pieces
Magnetic barrier, short 2 Pieces
Magnetic piston l Piece
Guide piece for magnetic piston l Piece
Hover discs 8 Pieces
Model simulation
Real Object Model
Vessel containing Experiment surface of
the gas the air-cushion table
surrounded by the
magnetic barriers and
the magnetic piston
Walls of the vessel Magnetic barriers
Piston limiting the Magnetic piston
volume of the gas
Gas molecules
Hover disc
How to proceed:
Align the air-cushion table horizontally and attach
the magnetic barriers. Place the piston on the
experiment surface parallel to magnetic barrier
no. 2. To provide a lateral boundary for the piston
rod and to ensure its successful guidance, place
the guide piece for the magnetic piston onto
barrier no. 2. Place the hover discs onto the
experiment surface near barrier no. 1 with the
slit for the airflow entering the experiment surface
from the side. Move the piston towards this
barrier as far as possible.
Turn the fan to a setting that provides a strong
airflow. Increase the mean velocity of the hover
discs by repeatedly opening the impulse valve
for a short period. Observe the motions of the
hover discs and the piston.
Result:
The piston shifts through the impacts of the hover
discs at the rate at which the mean velocity of the
hover discs rises. This causes an enlargement of
the area available to the hover discs.
Interpretation:
Increasing the temperature of a gas causes a rise
in pressure when the volume is constant. If the
vessel containing the gas is equipped with a mov-
ing piston, a rise in temperature will increase the
volume of the gas.
Note:
The force acting on the piston from the outside
due to air pressure can also be demonstrated in
this experiment by slightly tilting the experiment
surface so that the hover discs have to push the
piston up a slope.
2.1.13 Dependence of the Pressure on the
Number of Molecules
Components:
Air-cushion table with fan
Overhead projector
Magnetic barrier, long
2 Pieces
Magnetic barrier, short 2 Pieces
Magnetic piston l Piece
Guide piece for the magnetic piston l Piece
Hover discs
8 Pieces
Model simulation
Real Object Model
Vessel containing Experiment surface of
the gas the air-cushion table
surrounded by the
magnetic barriers and
the magnetic piston
Walls of the vessel Magnetic barriers
Piston limiting the Magnetic piston
volume of the gas
Gas molecules
Hover disc