Electric fields and conductors

[leelee]

Hi,
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 textbook 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, wouldn't 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?

thanks!

 

[Astronuc]

See if this helps.

http://hyperphysics.phy-astr.gsu.edu/hbase/electric/elesph.html#c2

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.

 

[quicknote]

I can confirm that your understanding is correct. In a conductor, the electric field is zero when charges are at rest. This means that there is no electric field within the metal part of the conductor, as well as the "empty" inside core of the conductor. However, if there are charges within the conductor, the electric field would exist within the conductor and radiate from those charges. This can then induce charges on the metal of the conductor, creating an electric field outside the conductor. The textbook example you mentioned about a positive charge within the conductor is a good illustration of this concept. It is important to note that the electric field within a conductor is only zero when charges are at rest, and if the charges are in motion, then there will be a non-zero electric field present within the conductor. I hope this clarifies your confusion about electric fields and conductors.