Charge on conducting and non-conducting body

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Discussion Overview

The discussion centers around the distribution of electric charge in conducting versus non-conducting bodies, exploring the underlying principles of electrostatics, including concepts such as electric fields, charge movement, and polarization. Participants examine why charge can be distributed throughout the volume of non-conducting materials while it is restricted to the surface of conducting materials.

Discussion Character

  • Technical explanation
  • Conceptual clarification
  • Debate/contested

Main Points Raised

  • One participant states that charge can be distributed throughout the entire volume of a non-conducting body, while in a conducting body, charge resides only on the surface, expressing confusion about this distinction.
  • Another participant explains that electric fields do not exist within conducting bodies because any existing fields would cause charges to move, thus canceling the fields. They reference Gauss's Law to support this claim.
  • A subsequent post reiterates the previous explanation regarding electric fields and charge distribution in conducting bodies, emphasizing the application of Gauss's Law.
  • In response to the initial confusion, a participant clarifies that in non-conducting materials, charges are bound to atoms and can create dipole moments under an electric field, leading to polarization, which allows for charge distribution throughout the volume.
  • Another participant expresses understanding of the explanation regarding charge distribution in non-conductors.

Areas of Agreement / Disagreement

Participants generally agree on the principles governing charge distribution in conducting and non-conducting bodies, but there remains some confusion and a lack of consensus on the underlying reasons for these differences, particularly from the initial poster.

Contextual Notes

Some assumptions regarding the behavior of charges in different materials are not fully explored, such as the specific conditions under which polarization occurs in non-conductors and the implications of charge movement in conductors.

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the charge on a body can be distributed throughout the entire volume only if the body is non-conducting,and the charge on a conducting body can reside only on the surface. I'm confused , why?
 
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All charges are surrounded by lines of force (electric fields). If there are charges iwithin conducting bodies, there are also electric fields. But electric fields don't exist in conducting bodies, because if there were, the charges would move (conduct) to cancel the electric fields. Therefore there are no free (excess) charges within conducting bodies. There can be charges on the inside surface of a conducting sphere, but only if there are matching free charges within the enclosed volume. Gauss's theorem in the conducting sphere (integral[E*n da] = integral [rho dv] = 0) requires no electric field within the conducting sphere, so no net enclosed charge. In short, use Gauss's Law.
 
Last edited:
Bob S said:
All charges are surrounded by lines of force (electric fields). If there are charges iwithin conducting bodies, there are also electric fields. But electric fields don't exist in conducting bodies, because if there were, the charges would move (conduct) to cancel the electric fields. Therefore there are no free (excess) charges within conducting bodies. There can be charges on the inside surface of a conducting sphere, but only if there are matching free charges within the enclosed volume. Gauss's theorem in the conducting sphere (integral[E*n da] = integral [rho dv] = 0) requires no electric field within the conducting sphere, so no net enclosed charge. In short, use Gauss's Law.

thanks... i got it ... but why can the charge be distributed throughout the entire volume only for a nonconducting body??/
 
Because the charges are generally thought of as being bound to the atoms/molecule that make up the bulk material. Certain things can happen, but only over a limited distance. For example, in a non-conducting dielectric, the field does not strip the electrons and moves them about like it can in a conductor, but rather it stretches the atom into a dipole moment. The electrons bunch in the direction of the electric field leaving the nucleus to move away. This results in a small dipole moment. Since the bulk's dipole moments will follow the field, you get polarization within the dielectric.

The charge gets distributed throughout by the fact that it is restricted from moving about the bulk, unlike in a conductor.
 
well ...yeah ..that makes sense...thanks.
 

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