  Students are taught several models of conductivity, both at the introductory
and the advanced level. From early macroscopic models of current flow in
circuits, through the discussion of microscopic particle descriptions of
electrons flowing in an atomic lattice, to the development of microscopic
non-localized band diagram descriptions in advanced physics courses, they need
to be able to distinguish between commonly used, though sometimes
contradictory, physical models. In investigations of student reasoning about
models of conduction, we find that students often are unable to account for the
existence of free electrons in a conductor and create models that lead to
incorrect predictions and responses contradictory to expert descriptions of the
physics. We have used these findings as a guide to creating curriculum
materials that we show can be effective helping students to apply the different
conduction models more effectively.
