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

In summary: When we release the charge, we see the metal move through the insulator.Charging by induction means the movement of charge is not caused by contact. It is caused by the magnetic fields around the charged object.
  • #1
manjuvenamma
102
0
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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  • #2
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"
 
  • #3
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.
 
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  • #4
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.
 
  • #5
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.
 
  • #6
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?
 
  • #7
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.
 
  • #8
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.
 

1) How do charges distribute on the outer surface of a conductor?

The charges on the outer surface of a conductor distribute evenly due to the principle of electrostatic equilibrium. This means that the electric field inside the conductor is zero, and all excess charges reside on the outer surface.

2) Why do only conductors have charges on their outer surface?

Conductors have free electrons that are able to move and redistribute themselves on the outer surface when in the presence of an external electric field. This allows the charges to be evenly distributed on the outer surface, while insulators do not have this ability and therefore cannot have charges on their outer surface.

3) Do all charged bodies have charges on their outer surface?

No, only conductors have the ability to redistribute charges on their outer surface. Insulators, on the other hand, have fixed charges that cannot move, so they do not have charges on their outer surface.

4) What happens to the charges on the outer surface when a conductor is grounded?

When a conductor is grounded, the excess charges on the outer surface flow into the ground, leaving the conductor with a neutral charge. This is because the ground acts as an infinite reservoir for charges, so it can absorb any excess charges from the conductor.

5) Can a conductor have charges on both its inner and outer surface?

Yes, it is possible for a conductor to have charges on both its inner and outer surface. This can occur if the conductor is not in electrostatic equilibrium, meaning that there is an unbalanced external electric field acting on the conductor causing the charges to redistribute on both surfaces.

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