1. The problem statement, all variables and given/known data Put in plain words: "In a static situation, the electric field at the surface of a conductor can have no component parallel to the surface, because this would violate the condition that the charges on the surface are at rest." Would this same statement be a valid one for tha electric field at the surface of an insulator? 2. Relevant equations 3. The attempt at a solution I can't understand the sentence, and can't figure out if it's valid for an insulator.