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Talk:Faraday cage

The last part of this article is written in German!

The bit about holes is inaccurate: EM radiation with a wavelength comparable or smaller to the size of the hole gets through easily. That's why the mesh in microwave oven windows has to be so fine. The Anome

I think 'hole' refers to the inside, not to a hole in the mantle. Patrick 14:03 Nov 25, 2002 (UTC)

This whole article has a "subtly wrong" feel to it: it conflates several things as if they are one, such as:

  • ground plane
  • Faraday cage principle (exclusion of electric field)
  • preferential / sacrificial conductor
  • skin effect
  • RF shielding

Can people with a physics / EE background please take a look at the article and try to sort this out?

Perhaps we need to break this article into several sections:

  • Idealised Faraday cage
  • Mathematics of the Faraday cage
  • Faraday cage in practice
  • --> article on Electrostatic shielding and earthing
  • --> article on RF shielding and earthing

Starting to rework: but it's still wrong... hmmm... The Anome

"Since like electrical charges repel each other, they accumulate where they can be furthest apart, on the outside layer of the Faraday cage." ... This is a description of the electrostatic principle that the electric field inside a conductor is zero; it is not applicable to changing EMFs. I'm rewriting the paragraph... --hb

The excited fields oppose the applied fields, in concord with the law of conservation of energy.

The relationship is not clear to me. Patrick 11:11 Nov 26, 2002 (UTC)

a current that cancels the applied field inside the conductor

This may create the impression that as long as the electric field is outside, the current flows to cancel it inside; however, in the case of a static field, the charge distribution (+ here, - there) takes care of it, the current is there only very shortly to create this charge distribution. Patrick 11:56 Nov 26, 2002 (UTC)

I agree that the article seems to include stuff that isn't strictly within the original definition of the Faraday cage effect. I added some historical info at the beginning to show where the idea started. Perhaps with more research we can trace how the concept has been broadened to RF etc., and whether the later additions deserve to be part of this article. -- Heron

The concept doesn't have to be "broadened" to include RF. It includes all electrical energy. In practical F Cages, instead of smooth walls, a mesh is used to save metal/cost (or for visibility), and in that case the wavelength of the electrical energy becomes significant vis a vis the mesh size; obviously, the EM energy at the optical wavelengths are meant to get through. If the cage is completely closed and smooth (e.g., a closed sphere), classical EM theory predicts zero field inside everywhere. Of course, quantum considerations change everything...

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