If we consider solid conductors, then of course the atoms are tightly
bound to each other so that the current is carried by the negatively
charged electrons There are, however, other types of conductors like
electrolytic solutions where positive and negative charges both can move In our discussions, we will focus only on solid conductors so that the
current is carried by the negatively charged electrons in the background
of fixed positive ions Consider first the case when no electric field is present