Consider a conducting wire which has some electrical resistance connected across a source of emf (voltage). Presumably there must be an electric field within the wire to cause the movement of electrons, in fact the same field as exists outside the wire, between the terminals of the voltage source.
A) How does the internal field result in the progressive voltage drop (relative to the down-stream terminal) along the wire - what is the mechanism? Is it to do with a changing concentration of electrons?
B) why isn't the internal field zero, as in a closed metal container?