PX157 - B6a - conductors

static situation: in a conductor, $\vec{E} = 0$
if $\vec{E} \neq 0$ , free charges will move, which will inevitably cause them to collide with atoms. this will cause a resistive material to heat up
this implies that temperature is a function of time, hence it is not static
any excess charges on a conductor must be on the surface
- if the gaussian surface is inside he conductor:

\subset \supset \iint \vec{E} d \vec{S} = 0 ⟹ Q_{e n c l .} = 0

- if the gaussian surface is on the edge of the conductor:

\subset \supset \iint \vec{E} d \vec{S} \neq 0 ⟹ \frac{Q_{e n c l .}}{ϵ_{0}}