I have an old baby rattle that consists of six small balls inside a larger clear sphere. When at rest, the balls repel each other, and never touch. Assuming they are magnets, shouldn’t they immediately clump together?
Video: [https://www.reddit.com/user/PM_ME_YR_BOOPS/comments/gwammg/baby_rattle_with_magnets_that_only_repel/](https://www.reddit.com/user/PM_ME_YR_BOOPS/comments/gwammg/baby_rattle_with_magnets_that_only_repel/)
In: Physics
They are probably weighted on one side which causes the north and south pole to always be on the same side, causing them to always repel.
I believe the balls aren’t magnetic, they are electrets. They retain a static electric charge that is uniform within them. The balls are held apart by the ensuing electrostatic forces. This is the same effect makes plastic cling wrap work.
You can test this theory by bringing another statically charged object near them, like a balloon rubbed on hair. If the balls are electrets, they should be attracted/repelled away from the balloon.
Maybe it’s not a magnetic force but an electric one (static).
I’m not sure if that’s the case but if it is, all the balls have a positive charge (or all negative). Each ball produces an electric field which repels all other balls.
I’d bet the inside of the clear plastic shell is coated with something that produces the same electric field as the balls. The shells electric field would balance out the electric field instead of the balls repelling as far as possible. This means that the balls are suspended between each other and the shell rather than them being pushed up against the shell from the repulsion of the balls.
As I typed this I got more confident because the physics I know actually worked out and stuff so please let me know the real answer!!
EDIT: Also, you could test it by bringing it close to another electric field (possibly an old TV screen or something).
EDIT: Now that I’m thinking about it, I’m curious about the formations the balls took. First the triangle, then the hexagon type thing with an extra one at the top, then a hexagon type thing with one in the middle. If the electric field theory is right, I’d imagine more of a 3D object that would fit snugly within a sphere. The corners of the 3D object would be the balls. Something that can be inscribed within a sphere makes sense to me since it would be most similar to the shape of the shell. This is a really good question and I’m gonna be thinking about it for a while haha…
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