i encounter the concept of conductors first in electrostatics. In which they said that the electric field lines cannot pass through the conductor. The reason they give is there is an opposite electric field produce in a conductor when we apply a external electric field. Then they describe why the charges accumulate over a surface of conductor. but now as i'm studying electric current they said there is free electron present in a conductor which move through a body of conductor as we applied external field.now i want to understand how the mechanism of conductor works in the case of electrostatics and in the electric current. and how the free electron comes inside as the electric field is 0 in conductor.
In the cases covered by electrostatics, the electrons in a conductor respond to an electric field by redistributing themselves inside a conductor in such a way that the resultant electrical field inside the conductor is zero. It takes some time for the electrons to move to their new positions, but this is very short time.
In case of an electric current, the external voltage source keeps supplying electrons to one side of a conductor and removing electrons from another side. By doing so, it keeps breaking the balance achieved in the static case, which creates a net electric field inside the conductor, which is actually responsible for the current.
We can say that the electrons make a current by trying to reposition themselves in an attempt to kill the electric field inside the conductor, but the action of the voltage source keeps frustrating this effort by constantly supplying and removing electrons, and therefore, as long as the current flows, the net electric field inside the conductor persists.