Why would a plaster appear to be attracted to the body?

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Offline thedoc

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asked the Naked Scientists:
   Hi Chris,

I should listen more quickly and trust the audience more, though, since someone answered the question in the next episode! Thanks for making the show! I especially like when you talk about scientific results that have been established for a while. I'm listening from Kagoshima, Japan, by the way. Maybe you don't have that place on your list yet. And I have a question, too. A few days ago I injured my foot and had to use a plaster. I noticed that the plaster is drawn to the skin from a short distance (1 cm?) like a magnet is to metal. How can that be? It can't be electromagnetic and I thought intermolecular forces only act at a much shorter distance. And I'm certainly not heavy enough for noticeable gravitational attraction.

What do you think?
« Last Edit: 14/10/2016 14:23:02 by _system »


Offline alancalverd

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Re: Why would a plaster appear to be attracted to the body?
« Reply #1 on: 14/10/2016 17:32:29 »
When you strip the protective plastic off a plaster, you induce static charges on both, just like rubbing your hair with a balloon. Now you throw away the protective strip and you are left with a charged plaster that sees your body as a large, uncharged object - or you may even have acquired the opposite charge of the strip - so there is an electrostatic attraction between the plaster and the body.

Some patients notice an interesting phenomenon in an x-ray department: they say they can "feel the radiation". If you remove a synthetic gown, nylon shirt or Crimplene trousers (I'm going back to the Sixties here!) you will generate a considerable charge that will leave your body hair erect. The x-ray beam ionises the air around you and this can discharge your body, so you feel the odd sensation of all the hair relaxing.
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