Which wire insulation is indicated by 'X'?

The identification of wire insulation as 'X' corresponds to cross-linked synthetic polymers, which are commonly used in electrical wiring applications due to their superior thermal and electrical properties. Cross-linking enhances the material's ability to withstand higher temperatures and is resistant to chemicals, making it an ideal choice for various environments where electrical wiring is exposed to extreme conditions. This type of insulation provides excellent durability and flexibility, aiding in the prevention of electrical breakdowns and ensuring long-lasting performance.

In contrast, asbestos, while historically used for its fire-resistant properties, has largely fallen out of favor due to health concerns associated with its inhalation. Rubber insulation is known for its good flexibility and moderate thermal resistance, but it does not offer the same high-temperature capability as cross-linked polymers. Mineral insulated cables, typically employed in specialized applications requiring high fire resistance and lower smoke emission, utilize metals and are not as flexible as synthetic polymers.

Overall, recognizing cross-linked synthetic polymers as 'X' underscores their importance in modern electrical insulation technology, particularly in applications requiring reliability under demanding conditions.