The exhibit consists of a pair of magnets, a pair of wooden cylinders the same size and shape as the magnets, and five tubes. The rightmost tube is clear plastic, the next two are aluminum, and the left two are copper water pipe. The thinner copper pipe is the type that is used in houses, and the thicker copper pipe typically is used in commercial buildings. The magnets are covered with plastic tubing to minimize the chance of pinching a bit of skin between the magnets and to make it possible to pull the magnets apart. (The magnets are so strong that if opposite poles were allowed to come completely together it is very difficult to then separate them.) Magnets only attract iron. Hold the magnets against each of the pipes to confirm the magnetic field does not attract any of them. One would expect then that if the magnets were dropped down the pipes they would fall right through. Two magnets are provided so that one can compare how fast they fall through any two pipes. Try dropping one magnet through the plastic tube and at the same time the other magnet through any of the other tubes. For comparison, drop the two wooden cylinders through the same two tubes and observe the results.
In the GENERATING ELECTRICITY exhibit, the motor pulley is turned and electricity results. Inside the motor housing there are three "ingredients" that are all needed to make electricity - a permanent magnet, a coil of wire, and the rotating movement of the coil. Each of these ingredients is present when the magnet is dropped down the aluminum or copper pipe. (Both of these metals are conductors of electricity, so the pipe acts like a wire.) Therefore electricity is being created as the magnet drops down the copper or aluminum pipe.
Two rings of electricity are being created as the magnet falls down the pipe. One ring of electricity is at the bottom edge of the magnet and the other is at the top edge. Flowing electricity always creates an electromagnetic field, an electromagnet. The ring of electricity at the bottom edge of the magnet creates a magnetic field that opposes or pushes up against the falling magnet. The ring of electricity at the top edge of the magnet creates a magnetic field that attracts or pulls up on the falling magnet. These electromagnetic fields both oppose the direction of travel of the magnet and thus slow its fall. This interaction is called an Eddy Current or Eddy Effect. IS IT POSSIBLE TO MEASURE THE INDUCED ELECTRIC CURRENTS? Every house has an electric meter that measures the amount of electricity being used. In the lower portion of each meter is a thin aluminum disk that is always revolving. That disk is moving in a magnetic field so that there is always an eddy current trying to slow the disk down. This makes the meter more accurate.
Balances used in chemistry labs to measure small quantities will oscillate back and forth when first loaded. The user must wait until the balance stops oscillating. Better balances will have a thin disk or strip of aluminum or other metal within a magnetic field. The generated eddy current as the balance oscillates serves to naturally slow down or dampen this motion so that a reading can be made more quickly.