Impact of frequency on Faraday cages

In summary, Faraday cages are designed to block electromagnetic fields and are effective for high, very high, and microwave frequencies. They work by separating the charges inside the conductor to create an electric charge of 0. They are not effective for sound waves or other non-electromagnetic low frequency signals. However, for radio frequencies, they are the most effective way to block signals.
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stanley
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I've been reading about faraday cages. The way I see, it works because the condutor will separate the charges so that the eletric charge inside is 0.
Then I saw a lecture in which the professor was carrying a radio and the signal stopped as soon as he entered the cage however we were still able to hear him talking through the speakers, he said that's because the speakers were in a much higher frequency.
My questions are:
  • Why the fact that the eletric charge inside the condutor being 0 blocks electromagnetic fields?
  • Why aren't faraday cages effective for high frequency waves?
  • Why aren't they effective for very low frequencies?
  • Are there better ways to block low frequency waves than with a faraday cage?
 
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  • #2
stanley said:
Summary:: Faraday cages and low/high frequencies

I've been reading about faraday cages. The way I see, it works because the condutor will separate the charges so that the eletric charge inside is 0.
Then I saw a lecture in which the professor was carrying a radio and the signal stopped as soon as he entered the cage however we were still able to hear him talking through the speakers, he said that's because the speakers were in a much higher frequency.
My questions are:
  • Why the fact that the eletric charge inside the condutor being 0 blocks electromagnetic fields?
  • Why aren't faraday cages effective for high frequency waves?
  • Why aren't they effective for very low frequencies?
  • Are there better ways to block low frequency waves than with a faraday cage?
Welcome to the PF. :smile:

In one part of your question, you are asking about DC electric fields. In the next part of your post, you are asking about RF radio transmission fields.

Can you post a link to what you have been reading, and say what your end goal is in understanding this? What are you wanting to shield from what?

Thanks.
 
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  • #3
berkeman said:
Welcome to the PF. :smile:

In one part of your question, you are asking about DC electric fields. In the next part of your post, you are asking about RF radio transmission fields.

Can you post a link to what you have been reading, and say what your end goal is in understanding this? What are you wanting to shield from what?

Thanks.
Mostly here and here.

As for what I'm wanting to shield from, I just want to know when and WHY a faraday cage might not be able to completely block EM signals(i.e when the frequency is either too high or too low)
 
  • #4
stanley said:
Mostly here
The title of that article is nonsense, so I didn't bother reading any farther. Quiz Question for you -- why is that nonsense to try to talk about a Faraday cage shielding magnetic fields? Lordy.
Does a Faraday cage block all magnetic field frequencies lower than x?

stanley said:
and here.
Sorry, I don't usually bother with YouTube videos as scientific references. There are exceptions of course, but on basic stuff that you want to learn about, it's usually okay to start at Wikipedia:

https://en.wikipedia.org/wiki/Faraday_cage

Also, if you want to learn more about the shielding of RF EM fields, it's good to go to a website of a manufacturer of shielded enclosures:

http://www.ets-lindgren.com/solutions

The main issue for RF shielding is how seamless the metal shield is, especially for feed-throughs that need to go through the enclosure walls (like for power and communication wiring, HVAC, etc.), and for doors for access into the room. There are different ways to do the RF gasketing that is needed for such entry doors...
 
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stanley said:
Summary:: Faraday cages and low/high frequencies

Then I saw a lecture in which the professor was carrying a radio and the signal stopped as soon as he entered the cage however we were still able to hear him talking through the speakers, he said that's because the speakers were in a much higher frequency.

This really doesn't make sense as written and need for you to clarify

Did he have speaker(s) inside the cage playing music or something ?
If so, then the cage ISNT going to stop sound waves from coming out

Sound from speakers is MUCH lower than the radio frequency he would have been using
and Faraday Cages ONLY work on radio signals
stanley said:
Why aren't faraday cages effective for high frequency waves?

They are very effective at high, very high and right up to microwave frequencies when designed for the required frequency

eg. the grid shield on your microwave oven door very effectively stops 2.4GHz microwave radio signals from escaping

stanley said:
Why aren't they effective for very low frequencies?

as long as they are radio frequencies, they are effective
stanley said:
Are there better ways to block low frequency waves than with a faraday cage?

Again, Faraday Shields ( cages) are effective as long as it is for radio ( electromagnetic) signalsYou seem to have some misunderstandings around low and high frequencies and if they are electromagnetic or sound.
And that is what is causing your confusionDave
 

Related to Impact of frequency on Faraday cages

1. How does the frequency of electromagnetic waves affect the effectiveness of a Faraday cage?

The effectiveness of a Faraday cage is directly related to the frequency of the electromagnetic waves it is designed to block. The higher the frequency of the waves, the more difficult it is for the cage to block them. This is because higher frequency waves have shorter wavelengths, making it easier for them to pass through the holes in the cage's conductive material.

2. Can a Faraday cage block all frequencies of electromagnetic waves?

No, a Faraday cage cannot block all frequencies of electromagnetic waves. It is designed to block a specific range of frequencies, depending on the size and spacing of the conductive material used. Some cages may be more effective at blocking certain frequencies than others.

3. Does the thickness of the conductive material used in a Faraday cage affect its ability to block electromagnetic waves?

Yes, the thickness of the conductive material used in a Faraday cage can affect its ability to block electromagnetic waves. Thicker materials can block higher frequencies more effectively, while thinner materials may only block lower frequencies.

4. How does the size of a Faraday cage impact its effectiveness?

The size of a Faraday cage can impact its effectiveness in blocking electromagnetic waves. A larger cage will have more surface area for the waves to pass through, making it more difficult for them to penetrate. However, a smaller cage may be more effective at blocking higher frequency waves due to the shorter wavelengths.

5. Can the orientation of a Faraday cage affect its ability to block electromagnetic waves?

Yes, the orientation of a Faraday cage can impact its ability to block electromagnetic waves. If the cage is not properly grounded or if there are gaps in the conductive material, waves may be able to pass through. It is important to ensure that the cage is properly constructed and oriented for maximum effectiveness.

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