Magnets have been fascinating objects for people of all age groups. Like poles repel and unlike poles attract. That is the first lesson that we learn about magnets. But with combination of magnets, you can create regions where another test magnet can stay in stable equilibrium. Stable in the sense that if you displace the test magnet a little in any direction, the magnet comes back to its original position. Here is one attractive toy using a special configuration of the fields.
Magnetic Field, Stability.
A flat base, a pencil, three wooden cylindrical rods of length somewhat less than the length of the pencil, four ring magnets with diameter slightly more than that of the pencil.
Drill three holes in the flat base so that screws can be fixed in them. Drill small holes in the bottoms of the rods. Now fix the rods on the base using screws. Now take three magnets and keep similar poles upwards. Fix the magnets on the top of the rods using quick fix. Fix a ring magnet on the pencil again with the help of quick fix at the same distance from the tip. When placed on the tip, the four magnets should be at the same height and all the upward poles should be of same nature. Fix a two-blade wane on the top of the pencil. Now the apparatus is ready. Place the pencil vertically with its tip on the flat base, right at the center between the three rods. And it stands comfortably. Give a slight sideways push to the wanes to rotate it. The pencil will keep rotating for a long time. You can decorate the pencil so that when it rotates it shows interesting patterns.
The three magnets placed at the same horizontal level produce a magnetic field pattern which gives zero field at the center. Thus the magnet does not feel any magnetic force here. But that is as simple as placing the pencil on the tip without any magnet. Important point is that around the center, as you go slightly out of the plane the field increases symmetrically at all sides. The direction is such that it pushes the magnet on the pencil back towards the center. That provides stability and resists its toppling down
Inspired by www.arvindguptatoys.com