Which materials are commonly used as electrical insulators?

Electrical insulators are materials that resist the flow of electric current, making them essential for preventing unwanted conductivity in electrical systems. The correct answer identifies rubber, glass, plastic, and ceramics as commonly used electrical insulators because they possess high resistance to electric current, excellent dielectric strength, and the ability to withstand high voltages without breaking down.

Rubber is widely employed in insulation for wiring and electrical equipment due to its flexibility and durability. Glass is used in applications requiring high resistance and thermal stability, particularly in insulators for high-voltage transmission lines. Plastics are versatile insulators that come in various forms, such as PVC and polyethylene, and are commonly used in consumer electronics and electrical sheathing. Ceramics are excellent insulators at high temperatures and are used in applications like insulators in power lines, as well as in capacitors.

The other options include materials that do not exhibit the properties necessary for effective electrical insulation. For instance, metals like copper, aluminum, and steel are conductive and are used for wiring and connections, not as insulators. Wood, while having some insulating properties, is not reliable under varying conditions such as moisture, which can reduce its effectiveness. Silicon and graphite are semiconductors and conductors rather than insulators, while