E and M fields in a faraday cage

In summary, Faraday Cages blocks static electrical fields and their effectiveness depends on the frequency of the changing magnetic field. Typically, one would use mu metal at low frequencies and cages at high frequencies, with some overlap. Static magnetic fields can penetrate a Faraday cage if they are changing slowly, but not if they are changing quickly. Magnetostatic refers to static magnetic fields, while electrostatic refers to static electric fields. "Static" in this context means constant in time, not necessarily not moving. At low frequencies, mu metal shields are typically used in Faraday cages, while at high frequencies, cages are used. 60 Hz is considered a low frequency.
  • #1
Robismyname
14
0
I have a question regarding Faraday Cages...

Faraday Cages blocks static electrical fields

I read somewhere that static magnetic fields can penetrate the faraday cage when changed slowly. Faster changes in static magnetic fields cannot penetrate a faraday cage, is this true?

Also does Magnetostatic = static magnetic fields?

Does Electrostatic = static electric fields?
 
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  • #2
Farady cages block static electric fields not static magnetic fields. Their effectiveness depends on the frequency of the changing magnetic field. Typically, one uses mu metal at low frequencies and cages at high frequencies and there is considerable overlap.
 
  • #3
If the magnetic field is static then that means it does't move. So if it doesn't move that means that it can't pass through the cage correct? Or does static just mean slow moving?
 
  • #4
You should understand static to mean constant in time.
 
  • #5
Not to be a pain but I read a post from the Physics forum

( https://www.physicsforums.com/archive/index.php/t-12250.html) that suggest that

"Static electricity" can really only be defined one way: "charges that are not moving."

So I thought that Static Magnetic fields implied: "Magnetic fields that are not moving."

Thanks for the clarification...
 
  • #6
Robismyname said:
Not to be a pain but I read a post from the Physics forum

( https://www.physicsforums.com/archive/index.php/t-12250.html) that suggest that

"Static electricity" can really only be defined one way: "charges that are not moving."

So I thought that Static Magnetic fields implied: "Magnetic fields that are not moving."

Thanks for the clarification...

"constant in time" means dB/dt = 0. Saying that they do not change with respect to time is, IMHO, a little better way to say it than "not moving"
 
  • #7
When you say that "one uses mu metal at low frequencies" I assume you are talking about an inductor core made of mumetal powered by a low frequency power supply?

Would 60Hz Ac be considered a low frequency power supply?
 
  • #8
No. I meant a mu metal shield. Google "mu metal shield" for lots of good info. 60 Hz is usually considered low frequency.
 

1. What is a Faraday cage?

A Faraday cage is a structure or enclosure that is designed to block electromagnetic fields, also known as E and M fields. It works by using conductive materials to create a barrier that redirects the E and M fields around the outside of the cage, protecting the inside from any external interference.

2. How does a Faraday cage protect against E and M fields?

A Faraday cage works by creating a conductive shield around the interior of the cage. When an external E and M field is present, the conductive material of the cage creates an equal and opposite charge, canceling out the effects of the field inside the cage. This protects any electronic devices or sensitive equipment inside from being affected by the external E and M fields.

3. What types of materials can be used to build a Faraday cage?

A variety of materials can be used to build a Faraday cage, including conductive metals such as copper, aluminum, and steel. Conductive mesh or screens can also be used. It is important to ensure that there are no gaps or openings in the material, as this could allow E and M fields to enter the cage.

4. Can a Faraday cage protect against all types of E and M fields?

A Faraday cage is not 100% effective in blocking all types of E and M fields. Extremely low-frequency fields, such as those from power lines, may still be able to penetrate a Faraday cage. However, it is highly effective against higher frequency fields, such as those from cell phones and radios.

5. What are some common uses for Faraday cages?

Faraday cages have a variety of uses, including protecting sensitive electronic equipment from external interference, such as in hospitals or laboratories. They can also be used to block unwanted signals, such as in secure facilities or for military purposes. Some people also use Faraday cages to protect their personal electronic devices from hacking or tracking.

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