In the presence of an external electric field, insulators, also referred to as non-conductors, restrict the free movement of electric charges within them.

Insulators are materials characterized by their inability to permit the unrestricted flow of electric charges. When an external electric field is applied, the charges within the insulator do not drift towards the opposite charge. This phenomenon is primarily due to the strong atomic bonds that hold the electrons tightly to their respective atoms, thereby preventing their free movement.

To better understand the behavior of insulators under an external electric field, we can examine their atomic structure. In insulators, electrons are tightly bound to their atoms, making it difficult for them to migrate to neighboring atoms. This behavior contrasts sharply with that of conductors, where some electrons are loosely bound and can move freely. Consequently, when an electric field is applied to an insulator, the electrons remain tethered to their atoms instead of drifting toward the positive end of the field.

It is essential to note that although the charges within an insulator do not move freely, they still experience a force due to the external electric field. This force can induce a slight displacement of the charges, resulting in a phenomenon known as polarization. Polarization refers to the minor shift of charges within the insulator, which causes one side to become slightly more positive while the opposite side becomes slightly more negative.

In summary, insulators do not facilitate the free movement of charges when subjected to an external electric field. The charges within the insulator remain tightly bound to their atoms, preventing them from drifting toward the opposite charge. However, these charges do feel a force from the electric field, leading to a slight displacement known as polarization.