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I have read that if a charge was to be placed inside the cavity of a Faraday's Cage, its electric field would be canceled by the field applied by the interior surface of the cage's conducting material, therefore rendering the net electric field inside the cavity to be zero.

However, using this logic, I find it hard to understand why scientists often conduct experiments in rooms designed as Faraday Cages with electrical equipment, in order to reduce interference from external electric fields in their results. Wouldn't the net electric field inside the room be 0? Can someone please explain to me how electrical appliances can still operate inside such Faraday Cage rooms? Surely there must be electric fields inside the room for them to work?

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  • $\begingroup$ "I have read that if a charge was to be placed inside the cavity of a Faraday's Cage, its electric field would be canceled by the field applied by the interior surface of the cage's conducting material, therefore rendering the net electric field inside the cavity to be zero. You are misreading things. Either what you read is wrong or you are misreading what is written. Where is the sample charge really placed and where is the electric field measured? $\endgroup$
    – DKNguyen
    Sep 7, 2022 at 17:53
  • $\begingroup$ I read it on informit.com/articles/…. . Ok anyways, how would you say electrical appliances work inside a Faraday Cage? I am having problems understanding it, thank you $\endgroup$ Sep 8, 2022 at 5:23
  • $\begingroup$ Appliances work just like normal. All a Faraday cage can do is make internal electric fields not visible from the outside, or make external electric fields not visible from the inside. It does not magically nullify all electric fields inside to be zero. It's like how a soundproof box makes it so if you are outside you cannot hear what is inside, and if you are inside you cannot hear what it outside, but just because you can't hear the sound on the other side doesn't mean the there is no sound on the other side. $\endgroup$
    – DKNguyen
    Sep 8, 2022 at 13:33

2 Answers 2

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Can you use electrical appliances inside a Faraday's Cage?

Yes.

I have read that if a charge was to be placed inside the cavity of a Faraday's Cage, its electric field would be canceled by the field applied by the interior surface of the cage's conducting material, therefore rendering the net electric field inside the cavity to be zero.

No. It cancels the inside field of charges outside the cage. That's what it's good for: to prevent outside fields from affecting the stuff inside.

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    $\begingroup$ The answer to the title is "yes" $\endgroup$
    – anna v
    Sep 8, 2022 at 4:42
  • $\begingroup$ how so? can you please explain thank you $\endgroup$ Sep 8, 2022 at 5:25
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However, using this logic, I find it hard to understand why scientists often conduct experiments in rooms designed as Faraday Cages with electrical equipment, in order to reduce interference from external electric fields in their results.

I'm not an expert in this area, but I think you may be referring to an anechoic chamber which is used to test electrical equipment for electromagnetic compatibility (EMC).

It is my understanding that the base of the chamber is a Faraday cage lined on the inside by materials that absorb rather than reflect radio waves generated by the equipment being tested inside the cage. So the Faraday cage prevents waves from entering from outside while the lining prevents waves from being reflected on the inside, both of which would interfere with the test.

Hope this helps.

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