Pop Can

 

 

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.

 

 

Physics Lecture Demonstration Database

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