What defines a perfect insulator?

A perfect insulator is defined as a material that does not allow any electric current to flow through it. This means that when a potential difference is applied across a perfect insulator, no electrical energy can be transferred because there are no free charge carriers (such as electrons) available to move and carry the current. In practical terms, perfect insulators have an infinite resistance, making it impossible for current to pass through them under normal conditions. This understanding is fundamental in both electrical engineering and physics, guiding the selection of materials for various applications where preventing current flow is essential, such as in electrical insulation and safety measures.