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Thread: Can external current pass through Faraday cage,like thunder?

  1. #1 Can external current pass through Faraday cage,like thunder? 
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    Can external current pass through Faraday cage,like thunder? Will be there electrical field, inside the Faraday cage?


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  3. #2  
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    If you place a farady cage into an electrostatic field then all points of the cage will assume the same potential, proportional to it's position within that field. If you 'earth' the cage than that is the potential it will assume.

    THunder is sound.

    A Faraday cage is merely a screen or barrier to electromagnetic radiation, and, and a barrier to static electricity, the construction and mesh/or shield is varied according to it's desired use.

    The construction material will influence it's behaviour in a magnetic field (ie whether copper screened, steel plate etc.

    IF the design or materials are not properly chosen then the 'phenomina' of eddy currents can exist in the walls and re-radiate within the cage rendering it useless to certain frequencies.


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  4. #3  
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    I want to know what will happen if I insert current (moving electrons) into Faraday cage, which is ungrounded? Will still there be no electric field, inside the cage?
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  5. #4  
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    You will need to be a lot clearer with your question before a real answer can be given. How are you going to insert these electrons?
    What is the field strength? do you have a drawing, that shows th esystem and it's monitoring points?

    The way you phrase the question is incomplete, it is like asking "will another 10kilo's stop my car?"
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  6. #5  
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    Quote Originally Posted by Megabrain
    You will need to be a lot clearer with your question before a real answer can be given. How are you going to insert these electrons?
    What is the field strength? do you have a drawing, that shows th esystem and it's monitoring points?

    The way you phrase the question is incomplete, it is like asking "will another 10kilo's stop my car?"
    No matter how the field is strong, or how I will insert the current, it matter what will happen in Faraday cage.
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  7. #6  
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    OK then I'll give you a text book answer.

    In any place where an emf is sufficient to cause a detectable potential difference then an electrostatic field will be created, whether this is within a block of cheese or on the moon is irrelevant the, field will exist.

    So if your cage is large enough to contain a detectable electrostatic field and you insert one then yes.

    You should also consider that the Faraday cage is a barrier between two volumes, there is in theory no internal/external divide. Consider a cage expanding towards half the volume of the universe, on which side of any wall is 'inside' and which 'outside' ?
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  8. #7 im lost 
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    Okay, you guys have lost me there.

    What IS a faraday cage ? - Is it something similar to a capacitor ?
    The hand of time rested on the half-hour mark, and all along that old front line of the English there came a whistling and a crying. The men of the first wave climbed up the parapets, in tumult, darkness, and the presence of death, and having done with all pleasant things, advanced across No Man's Land to begin the Battle of the Somme. - Poet John Masefield.

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  9. #8  
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    Can I ask you some other question? What will happen, if I stand inside of ungrounded Faraday cage, and touch the metal from inside (which is not isolated with plastic or something), and in same moment lighting strikes, directly in the cage. Will I die?
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  10. #9  
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    A faraday cage is a square built of a metallic grid. If you're inside of it, then you are protected from voltages applied to it, because every point is at the same potential.

    Doesn't matter if it's grounded. If it is then then any applied voltage is shorted to ground, so there is zero potntial. If not, then every point is at the same potential, so you won't get shocked if you're inside.

    Should there be current flowing through it, there should also be no induced EM field inside. This is due to the grid construction. Apparently the fact that the current flows down and across negates any induced EM field -- I'm somewhat unsure of this point. However, Faraday cages are used as screen rooms for testing various radiating devices. We used to use them when setting up units that had transmitters and receivers. They prevented external interference to the receivers, and kept the transmitted energy in the screen room. ( They work both ways).

    Please note that if the current through the Faraday cage is excessive relative to its construction, things can break down. A direct lightning strike on a grounded Faraday cage, made of small gauge wire would probably cause failure in various segments. These would become progressively worse because the current carrying segments would become smaller as sectios failed. However, this is an extreme case

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