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I just watched this video where a guy uses magnetic "liquid metal" along with a standard magnet to create some pretty cool spiky shapes. The magnetized liquid, when brought near the standard magnet, makes a bunch of small spikes.

Why does this happen?

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Look up ferrofluids. – akhmeteli May 10 '15 at 6:50
i am assuming that you are talking about ferrofluid. ferrofluid consists of a ferric material suspended in an organic solvent. for more specific details you may wish to visit the chem SE – ziggy May 10 '15 at 9:57
The effect is called normal field instability. For a ferrofluid in a magnetic field the surface of least energy is not smooth, hence the spiky appearance when the neodymium magnet is brought near. I have to confess I don't know how to calculate the surface of least energy, though I suspect it is hard. – John Rennie May 10 '15 at 11:04
@JohnRennie I'd be tempted to use a relaxation iterative technique rather than trying for the analytic solution. – Carl Witthoft May 10 '15 at 11:22
Possible duplicates: , and links therein. – Qmechanic May 10 '15 at 11:34

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