"In a static situation, the electric field of a conductor can have no component parallel to the surface coz this would violate the condition that the charges on the surface are at rest." would this statement be valid for electric field at the surface of an insulator? Explain your answer and the reason for any differences b/w the cases of a conductor and an insulator. So, first I thought that this statement won't be valid coz charges can't move in an insulator but then I thought that these charges could be excess charges and not mobile charge carriers. So, the statement should be valid.