Which of the following are the three most common materials used for power cable insulation?

The focus is on understanding the materials most widely used for power cable insulation. Among the choices provided, the materials that stand out as the most common for this purpose include rubber, plastic, and thermoplastics. These materials are favored for several reasons.

Rubber is highly valued for its excellent insulation properties, flexibility, and resistance to environmental conditions. It's particularly useful in applications where cables may be exposed to physical stress or varied temperatures.

Plastic materials, including thermoplastics, are widely used due to their durability, resistance to moisture, and cost-effectiveness. They can be easily molded and are often utilized in a variety of cable types to enhance insulation and protection against mechanical damage.

While some of the other options include materials used in different applications, they do not commonly serve as standard insulation for power cables. For instance, mica and fiberglass are often used for high-temperature or specialized applications but are less prevalent in general power cable insulation.

Hence, the combination of rubber, plastic, and thermoplastics represents the mainstream choices for insulating power cables, ensuring safety and reliability in electrical systems.