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Homework Help: Electric fields and conductors

  1. Dec 4, 2005 #1
    I am confused about the electric field within a conductor.
    My textbook states that it is zero when charges at rest. Does this mean, the there is no electric field within the metal part of the conductor (let's assume this conductor is a hollow sphere), or the actual "empty" inside core of the conductor? Is the charge also inside the core of the conductor?? Because the text book then goes on with an example about a positive charge within the conductor, and how the lines from that positive charge would end on the negative charges on the inner surface of the conductor (this is induced) and therefore a postiive charge would be on the outter surface of the conductor. Thus now, a electric field would exist outside the conductor. However in this case, wouldnt there now be an electric field inside the conductor??
    So from this what i think is, if there are no charges within the conductor but there are charges outside of it, and they are not moving, then there is no electric field within the conductor. Howeever if there are charges within the conductor, then a field would radiate from that charge, and induce charges on the metal of the conductor, and the conductor would also create a electric field.
    Is this correct, or am i misunderstanding the text?

  2. jcsd
  3. Dec 4, 2005 #2


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    Staff Emeritus
    Science Advisor

    See if this helps.


    In a hollow conductor, the charges on the surface produce an electric field on the outside. but by Guass's law, E=0 inside.

    If the sphere is not hollow, but filled with a conductor or dielectric with a distributed charge, then there will be an electric field determined by the charge enclosed in the appropriate Gauss surface.

    Now what happens in a conductive material. Well in matter composed of atoms containing positive nuclei and negative electrons, charges are balanced. Excess charge may accumulate in the conductor, but since like charges repel, the charges in a conductor accumulate at the surface, which brings us back to the situation of a hollow sphere with a surface charge.
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