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Faraday cage (hollow conductors)

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Pepealej
#1
Feb25-13, 12:22 PM
P: 20
Hi! I have a question regarding the Faraday cage.

I know how a Faraday cage works and understand the principles that make it work and why (potential difference, flux, gauss' theorem...) but I have a question.

Why some Faraday cages work eventhough they have holes in their surface. For example, I have seen things similar to wire fences used as faraday cages (in experiments with Tesla coils), and they work.

Why? Does this mean that the conductor can have holes in it's surface and still the electric field inside it is still zero?

Thanks! :)
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marcusl
#2
Feb25-13, 01:47 PM
Sci Advisor
PF Gold
P: 2,080
It's a question of the frequencies that you want to block. Holes allow high frequencies to pass through, but the shield acts effectively as a solid to low frequencies. The pass-band transition frequency is primarily determined by the size of the holes.
Pepealej
#3
Feb25-13, 04:05 PM
P: 20
And which is the relationship between the size of the holes and the frequency?

marcusl
#4
Feb25-13, 04:09 PM
Sci Advisor
PF Gold
P: 2,080
Faraday cage (hollow conductors)

The specifics are complex and depend on hole shape, spacing, amount of metal between holes, etc. As a very rough rule of thumb, largest dimension of any opening must not exceed lambda/10 of highest frequency.
Menaus
#5
Feb26-13, 02:22 AM
P: 54
I think he may be asking why it works, not how.


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