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?
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
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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Update: June 2012