Charges on outer surface only for conductors or all charged bodies?

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Discussion Overview

The discussion revolves around the behavior of electric charge on conductors and insulators, specifically whether charge resides only on the outer surface of charged bodies and the implications of this for different materials. It includes theoretical considerations and clarifications about the properties of conductors and insulators.

Discussion Character

  • Conceptual clarification
  • Debate/contested
  • Technical explanation

Main Points Raised

  • Some participants assert that charge resides on the outer surface of charged bodies, questioning whether this applies only to conductors or to all charged bodies, including insulators.
  • One participant clarifies that there is no electric field inside a conductor and that the electric field at the surface is normal to the surface.
  • Another participant explains that in conductors, electrons repel each other and move to the surface to maximize distance, while in insulators, charges are less mobile and typically remain on the surface due to induced separation.
  • A participant expresses uncertainty about the claim that conductors cannot be charged by friction and seeks further clarification.
  • It is noted that surface charges on conductors can move freely, whereas charges on insulators are fixed in place, leading to different electric field behaviors.
  • Some participants discuss the possibility of charging insulators by induction and conduction, with differing opinions on whether insulators can be charged by these methods.
  • One participant defines charging by conduction as the transfer of charge through direct contact, which does not occur in insulators, emphasizing the need for insulation when handling charged conductors.

Areas of Agreement / Disagreement

Participants express differing views on whether insulators can be charged by induction or conduction, and there is no consensus on the claim that conductors cannot be charged by friction. The discussion remains unresolved regarding the specific charging mechanisms applicable to insulators.

Contextual Notes

Some claims about the behavior of charges on conductors and insulators depend on definitions and assumptions that are not fully explored in the discussion. The implications of charging methods and the conditions under which they apply are also not conclusively established.

manjuvenamma
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I read that charge resides on the outer surface of a charged (electrically) body. Is it meant only for charged conductors or all charged bodies including conductors or insulators? What are the specific points with respect to conductors and charges other than (i) conductors allow current freely (ii) conductors have no tangentical electric fiedl intensity E vector (iii) Conductors can not be charged by friction.
 
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For (ii) I would probably say "there is no E field inside the conductor and the E field at the surface of the conductor is normal to the surface"
 
that charge resides on the outer surface

It's for conductors. The electrons all tend to repel each other. Moving to the surface is the only way they can get as far from each other as possible. In a conductor, they are free to move. In an insurator, the electrons have much less ability to move. In an insulator, the charges are usually on the surface because you probably caused the separation of charge to occur at the surface, i.e., you rub the fur against the glass rod -- that's the outer surface of the fur rubbing against the outer surface of the glass rod. The charge sits there because it's an insulator. But a metal is different - the electrons can travel to the surface.
 
Last edited:
manjuvenamma said:
(iii) Conductors can not be charged by friction.

Is that right? I didn't know that. I would like to hear more about that.
 
Even for the charges on the surface a conductor behaves differently from an insulator. On a conductor any surface charges will move away from each other in order to spread out as much as possible. But charges on an insulator are stuck where they are and cannot move away from each other. This allows both a tangential E field at the surface and an E field within the insulator.
 
Yes, conductors can not be charged by friction. Please refer discussion on this point in this forum itself - raised by me earlier.

Now, can insulators be charged by induction and can they be charged by conduction?
 
manjuvenamma said:
Now, can insulators be charged by induction and can they be charged by conduction?
I don't think they can be charged by induction, but I do think they can be polarized by induction.

Any time anything is charged it is conduction (movement of charges) by definition.
 
Charging by conduction means transferring charge by touching. This does not happen in insulators. That is why we isolate charged conductors by covering them with insulators. In experiments, we hold the charged conductors/metals through insulator materials such as a plastic thread and wooden table.
 

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