Faraday cage (hollow conductors)

In summary, the question is about why some Faraday cages still work even with holes in their surface. The answer lies in the frequencies that the shield can block, with holes allowing high frequencies to pass through while acting as a solid to low frequencies. The relationship between hole size and frequency is complex and depends on various factors such as shape and spacing, but as a general rule, the largest opening should not exceed lambda/10 of the highest frequency.
  • #1
Pepealej
20
0
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! :)
 
Physics news on Phys.org
  • #2
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.
 
  • #3
And which is the relationship between the size of the holes and the frequency?
 
  • #4
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.
 
  • #5
I think he may be asking why it works, not how.
 

FAQ: Faraday cage (hollow conductors)

1. What is a Faraday cage?

A Faraday cage is a container made of a conductive material, typically metal, that is used to block external electric fields. It works by redistributing the electric charge on its surface to cancel out the electric field inside the cage.

2. How does a Faraday cage work?

A Faraday cage works by creating a barrier between the inside and outside of the cage, preventing external electric fields from passing through. When an external electric field comes into contact with the cage, the charges on the surface of the cage rearrange themselves to create an opposing electric field, effectively canceling out the external field inside the cage.

3. What are the applications of Faraday cages?

Faraday cages have a variety of applications, including protecting sensitive electronic equipment from electromagnetic interference (EMI), shielding electronic devices from lightning strikes, and preventing electronic eavesdropping.

4. Can any material be used to make a Faraday cage?

To be effective, a Faraday cage must be made of a conductive material, such as metal. Some materials, like aluminum foil, can also be used, but they may not provide as much protection as a solid metal cage.

5. Are Faraday cages 100% effective?

While Faraday cages are highly effective at blocking external electric fields, they are not 100% effective. In some cases, very strong electric fields or high-frequency electromagnetic waves may still be able to penetrate the cage. Additionally, gaps or holes in the cage can also reduce its effectiveness.

Similar threads

I Faraday cage made of a real conductor
Replies
3
Views
995
I Faraday cage continuity question
Replies
11
Views
1K
An electron inside a Faraday cage
Replies
13
Views
1K
Impact of frequency on Faraday cages
Replies
4
Views
2K
How do we show that the interior of a Faraday cage is an equipotential?
Replies
10
Views
1K
How does a Faraday Cage block electric fields?
Replies
8
Views
10K
Faraday cage in electrodynamics (with currents)
Replies
3
Views
1K
Does an iron ring shield a static magnetic field?
Replies
3
Views
2K
Electric Field Shielding: Does a Conductor Shield Inside?
Replies
4
Views
2K
What is the optimal thickness for a Faraday cage to attenuate radio signals?
Replies
12
Views
11K

Hot Threads

Recent Insights

Back
Top