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Faraday cage question

  1. Jan 18, 2008 #1
    Hi! 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?
  2. jcsd
  3. Jan 18, 2008 #2


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    If you mean put electrons onto a faraday cage then it will have a uniform charge distributed over the surface and so no difference in potential and so no electric field.
    If you mean put an electron inside a faraday cage then there is a field between the charged electron and whatever potential the cage is at.
  4. Jan 18, 2008 #3
    Nope - there will be no potential difference inside the cage meaning no electron movement meaning no current.

    So if you get hit by a lightning flying in an airplane nothing should happen - actually planes
    are often hit by lightnings.. the lightning just warps around the plane and continues down into the ground.. pretty cool.. :rolleyes:
  5. Jan 18, 2008 #4


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    The purpose of a Faraday cage is to isolate the stuff inside from the stuff outside. If you introduce currents inside the cage, the cage has no shielding effect.
  6. Jan 19, 2008 #5
    I mean if I insert current from outside, will it pass through the internal face? What will happen?
  7. Jan 19, 2008 #6
    isn't post #4 already stated clearly, the answer is no current inside ;)
  8. Jan 19, 2008 #7
    Can you explain what is happening, please? I sow this quote from wikipedia but can't understand:
  9. Jan 19, 2008 #8
    An external static electrical field will cause the electrical charges within the conducting material to redistribute themselves so as to cancel the field's effects in the cage's interior.

    Well, if my understanding did not fail me, what quoted from Wiki simply means, Instead of generating the E field outside of the cage, this time round, the E field is generated inside the cage when you put a charge inside the cage.
  10. Jan 19, 2008 #9
    Like this picture or?
  11. Jan 19, 2008 #10
    the E field is generated outside because of charge inside the cage, provided it is not grounded! ;) ;)
    hope you can get the picture
  12. Jan 19, 2008 #11
    How is that possible? The E field is generated outside because of charge inside the cage? Do you have some picture?
  13. Jan 19, 2008 #12

    if my understand from wiki is correct, lets hear what other might say on this. no picture here unfortunately.
  14. Jan 19, 2008 #13
    The above picture, wasn't correct?
  15. Jan 19, 2008 #14
    the above doesn't show any external E field. only when E field is present, the charges will redistribute itself, such that the effect is no E field inside the cage.

    you may wanna check out some electrostatic concept(induction) and Gaussian law in order to understand how the cage work. gtg.
  16. Jan 19, 2008 #15
    But man, we are talking about an excess of charges inside the cage. With inserting current, I also insert excess of charges, therefore, there must be somewhere excess of electric field.
  17. Jan 19, 2008 #16
    you can insert charge, but how you gonna insert current flow?
  18. Jan 19, 2008 #17
    Current flow, with lighting.
  19. Jan 19, 2008 #18
    no matter what u do, nothing would happen to you if you are IN THE FARADAY CAGE!!!
  20. Jan 19, 2008 #19
    That's the point. What is happening, so there nothing will happen you in the Faraday cage, if there is excess of charge?
  21. Jan 19, 2008 #20
    ALL the charge (the electrons) repel each other and try to move as far from each other as they can. They can move up to the sides, corners and outer faces of the cage, until then, they stay there.
    that's why no matter what u do, nothing would happen to you if you are IN THE FARADAY CAGE

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