Module 2 : Electrostatics
Lecture 8 : Properties Of Conductors
   Properties of Conductors
   A conductor (typically,a metal or ionic conductors like HCl or NaCl dissolved in water) allows free movement of charges,
The electric field inside a conductor is zero. In an equilibrium situation, there cannot be an electric field inside a
  conductor as this would cause charges (electrons or ions) to move around.
Charge density inside a conductor is zero. This follows from Gauss's law
 

\begin{displaymath}\nabla\cdot E = \rho/\epsilon_0\end{displaymath}

As $\vec E = 0$, the charge density $\rho=0$.
(This does not suggest that there is no charge inside, only that the positive and negative charges cancel inside a conductor.)

Free charges exist only on the surface of a conductor. Since there is no net charge inside, free charges, if
  any, have to be on the surface.
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