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Charge placed in a cavity in a conductor

  1. Oct 24, 2015 #1
    If a conductor has a cavity in it and if a charge is placed in the cavity, then will the electric feild inside it be zer
     
  2. jcsd
  3. Oct 24, 2015 #2

    berkeman

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    Staff: Mentor

    Welcome to the PF.

    The field inside the cavity will not be zero. Is there a reason that you think it would be zero?
     
  4. Oct 24, 2015 #3
    Actually I just started learning electrostatics. In our texts it is mentioned that electric feild inside a conductor must be 0. But nothing is mentioned if it has a charge inside it. So I just asked out of curiosity. Btw can you say why it wont be zero?
     
  5. Oct 24, 2015 #4

    berkeman

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    Staff: Mentor

    (I fixed "u" to "you" in your post -- we don't use text speak at the PF :smile: )

    There is a field because there is a charge (source of E-field) with no conductor shielding it from the space inside the cavity.
     
  6. Oct 24, 2015 #5
    "Inside a conductor" in this case should be read as inside the volume actually occupied by the conductor.
    It can also mean a hollow space surrounded by a conductor, in which the field is not necessarily zero.
    Suppose a charge q is in the hollow space
    On the inner and outer surfaces charges (-q and +q) are distributed such that the electric field inside the metal is cancelled.
    Outside the metal a field exists due to the outer surface charge distribution of +q. If the conductor and the cavity are spherical and concentric,
    this field will be equal to the field of a free charge.
     
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