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Charge inside a conductive shell

  1. Oct 27, 2008 #1
    Hi there , I'm a bit rusty on the subject so I have 2 questions , although they are quite similar.

    Anyways first one :
    Lets say i have a sphere charged with Q , and around that sphere I have a conductive shell (also a shpere) at some distance from our charged sphere . The conductive shell is ungrounded. So my question is this , would there be an electrical field outside of the conductive shell ?

    personally i think there would be a field outside , and only if the shell was grounded there'd be no field outside (because then the shell would recieve a -Q charge and it would nullify any field outside).

    Second question:
    Lets say we have an infinate conductive surface , the surface is ungrounded. and below that surface at a distance 'h' we have an infinate wire with a linear charge charge density of D. so my question is quite similar.

    so the question is ,would there be an electrical field above the surface , also if not or if yes , would there be a mirroring effect (i've translated it from a diffrent language so not sure if its the same in english so i'll explain). mirroring effect - basically we treat it as if there is another wire at the same distance behind the conductive surface , the field behind the surface is zero , but below it we look at the electrical field as if its a result from two wires.

    and to make things easier to understand , assuming i'm not too good at explaining , i drew some pictures :P http://img98.imageshack.us/my.php?image=pewpewpewhe6.jpg

    anyways here again i have my idea but since i havent touched the subject in quite a while im not sure.
    i think that there isnt mirroring effect unless the conductive surface is grounded (because only then it recieves an actual charge) and i see no reason that the conductive surface would block the electrical field above it

    dont know if it may seem like a homework question , but its more of a theoretical question for myself.
  2. jcsd
  3. Oct 28, 2008 #2


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    Homework Helper

    Yes, there will be an external electric field. Gauss law says so.

    Yes there will be an electric field. You can evaluate it by invoking the method of images. The conductive plate doesn't have to be grounded.
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