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Everyone knows this experiment: You mix salt and pepper and use a charged balloon to separate the pepper from the salt.

I never really understood how this works. In school (long time ago) we learned that unlike charges attract each other while like charges distract each other. In the experiment the negatively charged balloon attracts the pepper. Does this mean the pepper has a positive charge?

Why is pepper charged? How can I predict for given particle if the balloon will attract, distract or not interact with it?

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Promoted from a comment that should have been posted as an answer:

No, it is about mass to surface area ratio. The charged balloon induces polarisation on the salt and the pepper, but the salt is too heavy for this tiny separation, and thus tiny attractive force, to overcome weight, whereas the pepper is light enough for that to happen. The salt, being made of ionic bonds, is properly stronger polarised than the pepper, but the density difference is big enough. Note that neither salt nor pepper become charged; it is just that the charges separated in position just a little, so that the closer one is attracted more than the farther one is repelled.

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  • $\begingroup$ The pepper and the salt ions feel the same gravitational acceleration. $\endgroup$
    – Cerise
    Commented Oct 18, 2023 at 6:04
  • $\begingroup$ Thanks a lot for this answer, very good explanation. $\endgroup$
    – flappix
    Commented Oct 18, 2023 at 19:00

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