When an electric field is applied to a conductor versus an insulator, how do the charge distributions differ in each material?

When you put a conductor in an electric field, the free electrons inside the metal move almost instantly until they stop the field inside the metal. They pile up on the outer surface so that the electric field inside the conductor becomes zero. In an insulator, the atoms have no free electrons, so the charges cannot move; instead, each molecule is slightly shifted, creating tiny dipoles that align with the field but leaving the material overall neutral. Thus, a conductor ends up with a clear separation of charge on its surface, while an insulator develops only a small internal polarization. For example, a metal plate in a field will show a positive charge on one side and negative on the other, whereas a glass rod will only have its molecules slightly twisted, showing no net surface charge.