Final answer:
The historically first and still common material for high-voltage cable insulation is oil-impregnated paper. Advancements in material science suggest high-temperature superconductors could be used for efficient power transmission, if their current brittleness can be overcome. Meanwhile, copper remains a staple for wiring due to its electrical and physical properties.
Step-by-step explanation:
The impregnated material used for the insulation of transmission cables, which has historically been one of the first materials employed for this purpose and is still predominantly utilized in high-voltage cables, is paper soaked in oil or special compounds. This material has exceptional electrical and physical properties that make it suitable for high-voltage insulation. However, advances in materials science are leading researchers to explore high-temperature superconductors for power transmission. While superconductors offer the potential for transmitting electricity with no power loss due to resistance, their brittle and fragile nature currently limits their commercial application.
Despite these limitations, the first project demonstrating the viability of high-temperature superconductor power transmission was established in New York in 2008. In standard power transmission, ceramic insulators and glass insulators are commonly used to support high-voltage lines (e.g., 240-kV lines) and provide excellent resistance, often in the range of 1.00 × 10⁹ Ω each, preventing current from flowing through the insulators to the grounded metal towers.
For wiring applications where flexibility and durability is required, copper is widely used due to its low resistivity, high tensile strength, and high ductility. Different metals such as silver and aluminum are also used as conductors, while insulating materials generally include plastics, glass, ceramics, and wood.