 |
 |
In this exhibit, we can see the mystery of the rotating pop can that act at a distance.
To begin press the bottom “START”. Use the aluminum bar to cover 2/3 of the surface of the magnet pole face and observe as the can begins to rotate.
NOW AN EXPLANATION ON HOW THIS WORKS
1- The magnet produces an alternating magnetic field
2- Initially the rising magnetic field from the magnet induces currents in metallic objects (the can and the aluminum bar).
3- These currents generate magnetic fields in the opposite direction so that the objects are repelled.
4- Next, when the field reaches its maximum value, its rate of change becomes zero. The induced field becomes also zero.
5- The can becomes quickly demagnetized because it is thin.
6- But the current in the thicker aluminum bar continues longer, so the aluminum bar remains magnetized for a little while.
7- Next the field of the magnet begins decreasing; it induces a field in the opposite direction. The can gets magnetized the new way, but the aluminum bar retains the “old” magnetization and attracts the magnetized can.
8- Voila! rotation begins
You can try changing the position of the aluminum bar
You can also try using other metal sheets from the table.