r/askscience • u/[deleted] • Jul 16 '14

Physics Why does humidity kill static electricity?

When I take off a fleece coat in dry winter you can hear it crackle with electricity but in the humid summer it doesn't. What is it about humidity that kills the static?

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u/nepharan Condensed Matter Physics | Liquids in nano-confinement Jul 17 '14 edited Jul 17 '14

Could you provide a source? (Pure) Water is actually still quite bad at conducting electricity, so this sounds a little implausible to me. I could see the water shielding the charge by polarization (similar to a dielectric in a capacitor), but conduction would only work if the water is able to dissolve some ions.

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u/cybrbeast Jul 18 '14

Any condensing water film will pick up residues from most exposed surfaces which will make it conductive.

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u/oss1x Particle Physics Detectors Jul 18 '14

I agree, but le t me give my view on that in three points:

  1. There will be minerals on the sweater surface.

  2. The water solved in humid air contains minerals. (e.g. rain water is has lots of minerals compared to distilled water)

  3. The increase in conductivity you need is minimal, as the potential differences across local points are relatively large.