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Name: srividya
Status: student
Age: 17
Location: N/A
Country: N/A
Date: 2000-2001


Question:
why is it said that a conductor cannot store charges in them because i have heard that for analysis we consider uniform distribution of charges on the surface of conductors?


Replies:
Srividya,

This problem is mostly a question of vocabulary. A conductor cannot store charge IN it, but it can store charge ON it. Charge IN the conductor is inside the conducting material. Charge is free to move within a conductor. If some charge is positive and some is negative, opposites will move toward each other, joining into neutral atoms until only one kind remains. When all excess charge is of one sign, they will push each other away. They move freely away until they reach the surface. In a very short time, all excess charge has moved to the surface. It is ON the conductor.

Dr. Ken Mellendorf
Illinois Central College


Conductors, electrostatically, cannot have any net charge in any internal region. This can be proven with a simple bit of logic. If there were a net charge inside a conductor, it would exert a force on nearby charges, which in a conductor would cause them to move. Therefore, this is not a static situation. If one waits, the charges will all be pushed to the surface of the conductor and arranged such that there is no electric field inside and the electric field at the surface is normal to the surface of the conductor.

Then the charges inside will feel no force and so will remain at rest and the forces at the surface witll feel a force pushing them out of the conductor, where they are not free to go. Ergo, everything is stationary!

Note that in a insulator where the charges are not free to move, this argument does not work and so insulators can store net charges inside.

Best, Dick Plano



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