conduction current flows in a good
conductor, e.g., a metal. The current
then consists of free electrons which
are the charge carriers. Its strength is
determined by the electrical
conductivity of the material through
which the current flows. The
displacement current can exist in all
materials, whether conducting or non-
conducting. Consider a non-
conducting material like wood or
glass, placed in an electric field. There
are no free electrons in glass and so
conduction current does not exist.
However, the electric field leads to
some realignment of charges inside
the material. Electrons, though bound
to the atoms, are displaced slightly
opposite to the direction of the
electric field. The material thus gets
polarized. If the electric field is
switched off, the electrons go back to
their original configurations. If the
electric field changes direction
repeatedly, the electrons move slightly
to and fro inside the material with the
changing electric field. This slight
movement of electrons constitutes the
displacement current. Its strength
depends on the frequency with which
the electric field changes. The
existence of displacement current was
theoretically proposed by Maxwell
and is incorporated in his equations of
electromagenetism