PHYSICAL EXPERIMENTS ON THE AIR-CUSHION TABLE U15420
Physical Experiments on the Air-Cushion Table Table of Contents Introduction ........................................................................................................................ 5 1. Setup and Possible Uses of the Air-Cushion Table ........................................................... 6 1.1 1.2 1.3 1.4 1.5 Components of the experimenting apparatus ......................................................................... 6 Principle Uses of the Air-Cushion Table ................
Physical Experiments on the Air-Cushion Table 2.3 2.3.1 2.3.2 2.3.3 2.3.4 Structure and Properties of Solids ...................................................................................... 34 Configuration and Motions of the Lattice Elements in a Solid ............................................. 34 Melting a Solid .......................................................................................................................
Physical Experiments on the Air-Cushion Table Introduction lent visibility make this demonstration a kind of “window into the microcosm”. However, it is necessary to mind the shortcomings and limits of modeling. Not only are the procedures highly simplified and represented in a purely mechanical way, also the motions of the real objects are in many cases determined by other forces. Furthermore, all procedures occur on one level. Finally, models contain additional misrepresentations, which become visible e.
Physical Experiments on the Air-Cushion Table 1. Setup and Possible Uses of the Air-Cushion Table 1.
Physical Experiments on the Air-Cushion Table Item Quantity Plexiglas plate 1 Magnetic barrier 253 mm (no. 3 and no. 4) 2 Magnetic barrier 233 mm (no. 2) 1 Magnetic barriere 233 mm with slit for airflow from the side (no.
Physical Experiments on the Air-Cushion Table Item Quantity Flat magnetic barrier 1 Magnetic barrier made of 4 magnets 1 Electrodes 2 Manipulating rod 1 Magnetic hover disc Ø 16 mm, red 30 Drawing 8
Physical Experiments on the Air-Cushion Table Item Quantity Magnetic hover disc Ø 16 mm, green 25 Magnetic aluminum hover disc, Ø 21 mm 5 Magnetic hover disc Ø 28 mm, orange 25 Magnetic hover disc Ø 48 mm, blue 2 Magnetic piston 1 Drawing 9
Physical Experiments on the Air-Cushion Table Item Quantity Guide piece for the magnetic piston 1 Fastening screws for the holding device 2 Plastic tweezers 1 Aufbewahrungskasten 1 Drawing 10
Physical Experiments on the Air-Cushion Table 1.2. Principle Uses of the Air-Cushion Table chamber where the impulse valve is located is connected to the fan using the tube. The experiment surface can be set to the horizontal or inclined position by means of two adjusting screws. . . Five different types of hover discs are supplied with the air-cushion table. They are made of colored, transparent plastic or aluminum discs, onto which cylindrical, ceramic magnets are attached.
Physical Experiments on the Air-Cushion Table 1.4. Instructions for Usage The air-cushion table is placed onto the overhead projector so that the arrow on the pressure chamber points to the projection screen. The magnetic barriers (fig. 1) are placed onto the air-cushion table so that their numbers (no. 1 to no. 4) match the markings at the edges of the experiment surface. The magnetic barrier with the slit at the bottom is arranged at the side of the table where the tube of the fan connects.
Physical Experiments on the Air-Cushion Table be positioned behind the experimenting table or inside it. This will reduce the noise level reaching the classroom. Further noise reduction can be reached by wrapping sponge rubber around the fan or lining it with Piatherm or the like. Special care should be taken, though, to ensure that the air can enter the suction nozzle unimpeded. - Avoid damage caused by dropping, hitting, bumping, dragging or sliding. - Keep all parts clean and free from dust.
Physical Experiments on the Air-Cushion Table 2 Description of the Experiments 2.1 Structure and Properties of Gases 2.1.1 Motion of a Molecule in High Vacuum Components: Air-cushion table with fan Overhead projector Magnetic barrier, long 2 Pieces Magnetic barrier, short 2 Pieces Hover discs l Piece 2.1.
Physical Experiments on the Air-Cushion Table Note: This experiment can be developed from the one described above in 2.1.1. by placing three additional orange hover discs onto the experiment surface one after the other while keeping the fan turned on. The collisions between the discs and the transfer of kinetic energy caused by them can be especially well observed when using a low number of discs. 2.1.
Physical Experiments on the Air-Cushion Table Then reduce the area available for the hover discs to half its size. To do this, lift up magnetic barrier no. 2 and reattach it so that it separates the experiment surface into two halves, with its ends snapping into the recesses provided in barriers no. 3 and no. 4. Now set both hover discs into motion in the same way.
Physical Experiments on the Air-Cushion Table causes only a change in direction, a collision of two hover discs usually causes a change in speed as well. At any given point in time, the majority of the hover discs move at a mean velocity. Only few hover discs have a high and few a very low velocity.
Physical Experiments on the Air-Cushion Table Model simulation Real Object Model Vessel containing Experiment surface of the gas the air-cushion table Walls of the vessel Magnetic barriers Gas molecules Red hover disc with small mass Gas molecules Orange Hover discs with large mass Result: The mean velocity of the orange hover disc is much lower than the mean velocity of the red ones.
Physical Experiments on the Air-Cushion Table the resulting temperature is between the two initial temperatures. The reason for this is that the molecules of the gas with the higher temperature transfer part of their kinetic energy to the molecules of the gas with the lower temperature.
Physical Experiments on the Air-Cushion Table attach the magnetic barriers and spread the red hover discs evenly on the experiment surface. Provide an airflow just ensuring that all hover discs lift off. This keeps the mean velocity of the red discs low. Shortly afterwards, make the 4 green hover discs shoot between the red ones at the highest possible speed. This can be done in quick succession from one corner, using the pointer to hold each hover disc directly in the corner and then quickly releasing it.
Physical Experiments on the Air-Cushion Table Note: The experiments can be repeated using different initial positions of the piston and different mean velocities of the hover discs. The more closely the discs are arranged at the beginning and the higher their mean velocity is, the quicker they will fill out the entire area. between them are approximately 2.5 cm. Then increase the fan setting so that all hover discs are floating properly.
Physical Experiments on the Air-Cushion Table velocity of the molecules and the number of impacts. 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.
Physical Experiments on the Air-Cushion Table How to proceed: Align the air-cushion table horizontally and attach the magnetic barriers around the experiment surface. Arrange the piston parallel to magnetic barrier no. 2. The piston rod rests on the guide piece for the magnetic piston, which has been attached onto magnetic barrier no. 2 and ensures its guidance. Arrange three of the hover discs near barrier no. 1, the barrier with the slit for air entering from the impulse valve.
Physical Experiments on the Air-Cushion Table Result: After removing the partition, the hover discs mix evenly as a result of their own motions. This will occur more rapidly the higher the mean velocity is.
Physical Experiments on the Air-Cushion Table in the other. After turning the fan on, observe the movement of the hover discs through the opening. Increase the mean velocity of the hover discs by repeatedly opening the impulse valve for a short time. 2.1.
Physical Experiments on the Air-Cushion Table Result: The red discs hit the blue one at irregular intervals, setting it into motion. Its speed and direction of velocity change permanently, resulting in a zigzag path. Its average speed over time is much lower than that of the red discs. barriers. Turn the fan to a medium setting. Use the adjusting screw on barrier no. 4 to tilt the experiment surface of the apparatus more and more towards the projecting wall.
Physical Experiments on the Air-Cushion Table and finally, considerably less often, the 4:0 and 0:4 distributions. The frequencies of the 3:1 and 1:3 distributions are approximately equal, as are the 4:0 and 0:4 distributions. 2.1.
Physical Experiments on the Air-Cushion Table Table 1 Distribution Relative frequency in % 0:4 1:3 2:2 3:1 4:0 5 20 49 21 5 Relative frequency in % 40 20 0 0 : 4 1 : 3 2 : 2 3 : 1 4 : 0 Distribution Fig.
Physical Experiments on the Air-Cushion Table 2.2 Structure and Properties of the Liquids 2.2.1 Configuration and Motion of Molecules in a Liquid Components: Air-cushion table with fan Overhead projector Magnetic barrier, long Magnetic barrier, short Hover disc, orange on between the other discs. The kinetic energy differs from disc to disc and changes from time to time in each disc. The hover discs are irregularly arranged at short distances.
Physical Experiments on the Air-Cushion Table Model simulation Real Object Model Vessel containing Experiment surface of the liquid the air-cushion table Walls of the vessel Magnetic barriers Molecules of Red hover discs one liquid Molecules of the Green hover discs other liquid How to proceed: Align the air-cushion table horizontally and place the magnetic barriers on the experiment surface.
Physical Experiments on the Air-Cushion Table Interpretation: If a liquid contains microscopically small particles the thermal motion of the invisible molecules sets them into an irregular motion which can be observed under the microscope. 2.2.4 Brownian Motion in a Liquid Components: Air-cushion table with fan Overhead projector Magnetic barrier, long 2 Pieces Magnetic barrier, short 2 Pieces Hover disc, orange 25 Pieces Hover disc, blue l Piece 2.2.
Physical Experiments on the Air-Cushion Table The larger the mean velocity of the hover discs is, the faster individual discs will leave the original section. How to proceed: Align the air-cushion table horizontally and attach the magnetic barriers. Place the piston on the experiment surface right next to barrier no. 2. The guide piece for the magnetic piston placed onto magnetic barrier no. 2 ensures excellent guidance of the piston rod. Arrange the magnetic hover discs near barrier no.1.
Physical Experiments on the Air-Cushion Table the magnetic barriers. Spread the hover discs evenly across the experiment surface. Adjust the airflow strong enough to ensure that the hover discs lift off even when the impulse valve is opened. Briefly open the impulse valve several times so that the hover discs have a high mean kinetic energy. Observe the motions of the hover discs. occasional exchanges of position. Finally, each hover disc only moves around its own equilibrium position.
Physical Experiments on the Air-Cushion Table 2.3 Structure and Properties of Solids 2.3.1 Configuration and Motions of the Lattice Elements in a Solid Components: Air-cushion table with fan Overhead projector Magnetic barrier, long 2 Pieces Magnetic barrier, short 2 Pieces Hover disc, orange 25 Pieces Interpretation: The lattice elements in a solid are arranged in a regular configuration. They perform irregular oscillations around their equilibrium position.
Physical Experiments on the Air-Cushion Table Model simulation Real object Model Vessel containing Experiment surface of the gas the air-cushion table Walls of the vessel Magnetic barriers Piston in the vessel Magnetic piston Gas molecules Hover discs Result: Initially, the hover discs are arranged regularly and perform oscillating and circular motions around their respective location. Then the amplitudes of their oscillations increase. Individual discs change their position.
Physical Experiments on the Air-Cushion Table Interpretation: An increase in pressure and a drop in temperature will transform a gas from the gaseous to the liquid aggregation state. While the molecules perform translational movements in the gaseous state, the prevailing motions in the liquid state are oscillations, superimposed by few translations. In the solid state, the lattice elements are arranged in a regular configuration. They perform oscillations around their equilibrium position. motion.
Physical Experiments on the Air-Cushion Table 2.4. Processes of Electric Conduction 2.4.1 Motion of an Electron in a Vacuum Under the Influence of an Electric Field (Demonstrated By Means of Mechanical Forces) Components: Air-cushion table with fan Overhead projector Magnetic barrier, short 1 Piece Hover disc, orange 1 Piece Interpretation: The motion of electrons in an electric field is accelerated, provided that no other forces act on the electrons.
Physical Experiments on the Air-Cushion Table zontal position using the spirit levels. Arrange the electrodes at the edges of the experiment surface parallel to each other. The electrode on side no. 2 is set on its bases, whereas the bases of the other electrode point upwards. Place the magnetic barrier, turned by 180°, closely to the experiment surface parallel to the electrode on side no. 2, so that the hover discs cling to it due to the magnetic attraction.
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 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 influence of the electric field.
Physical Experiments on the Air-Cushion Table motions. Then place the orange disc onto the Plexiglas plate above the center of the experiment surface. Its magnet should face downwards so that the aluminum discs are repelled. Set the Plexiglas plate to different heights to vary the influence of the orange disc on the aluminum ones. Observe their motions. 2.4.
Physical Experiments on the Air-Cushion Table range the magnetic barriers around the experiment surface. Attach the holding device to the air-cushion table and insert the lattice model. Set it to its highest position. Place the hover discs onto the experiment surface. Turn up the fan so that all hover discs move freely on the air-cushion table. Observe their motions and interactions with the magnets of the lattice model. hover disc in such way that the mean drift velocity is constant.
Physical Experiments on the Air-Cushion Table 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 Interpretation: To enable the electrons to escape the surface, they have to possess a specific minimum energy. This corresponds to the work of escape.
Physical Experiments on the Air-Cushion Table Position the orange disc in a corner of the experiment surface and hold it with the finger at first. Then release it and observe the changes caused by this hover disc. Result: The orange disc moves across the experiment surface in a disorderly fashion, driving some of the red discs from their positions. These discs then move between the other bound discs as well, but return to fixed positions after a certain period of time.
Physical Experiments on the Air-Cushion Table 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 rise in temperature, so that they move throughout the semiconductor. The released electrons leave behind positive “holes”. The number of migrating electrons and the number of holes are equal.
Physical Experiments on the Air-Cushion Table How to proceed: Align the air-cushion table horizontally and attach 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.
Physical Experiments on the Air-Cushion Table 2.5 Nuclear Physics 2.5.1 Scattering of Positively Charged Particles Near an Atomic Nucleus Components: Air-cushion table with fan Overhead projector Holding device Plexiglas plate Hover disc, orange 5 Pieces Result: The hover disc changes its direction of motion near the stacked magnets. This change in the direction of motion is stronger the lower the velocity of the hover disc is and the closer the path runs along the stacked discs.
Physical Experiments on the Air-Cushion Table How to proceed: Align the air-cushion table horizontally. Attach the magnetic barriers and the holding device to the air-cushion table. Insert the Plexiglas plate and position it closely above the experiment surface. Place the orange disc in the middle of the Plexiglas plate. Turn the fan to a setting in which the red disc is sure to lift off. Use the manipulating rod to move it under the orange disc on the experiment surface. Observe its motions.
Physical Experiments on the Air-Cushion Table 2.6 Mechanical Motions 2.6.
Physical Experiments on the Air-Cushion Table Turn the fan to a medium setting. Set two stacked discs into slow motion starting from the edge of the experiment surface. Select a direction ensuring that it will float along the stacked discs at a distance of a few centimeters. Repeat the experiment several times, gradually reducing the shortest distance between the moving and the stacked discs. Observe the motion of the hover discs.
Physical Experiments on the Air-Cushion Table • • • • The instructions provide an overview of the main uses of the air-cushion table. The selection and configuration of the experiments used for teaching purposes shall be determined by the instructor. The physical interpretation of each experiment is given on a simple level, in accordance with the usually rough model illustration. The air-cushion table is a suitable teaching aid from the high school to the university level.
