Which type of material is typically used as an insulator in electrical wiring?

The use of plastic as an insulator in electrical wiring is primarily due to its excellent electrical insulating properties. Plastic materials, such as PVC (polyvinyl chloride) or polyethylene, have a high resistance to electrical current, which prevents the flow of electricity outside the intended conductor. This characteristic is crucial for safety, as it minimizes the risk of electrical shocks, short circuits, and electrical fires.

In addition to their excellent insulating properties, plastics are also lightweight, durable, and resistant to moisture and chemicals, making them ideal for various applications in electrical wiring. They can effectively cover and protect copper or aluminum conductors, which are the materials commonly used for conducting electricity. This combination ensures that the electrical system operates efficiently while keeping safety standards intact.

The other materials in the options have conductive properties (like copper and aluminum) or are used for structural purposes (like steel) and do not serve the insulating role needed in electrical applications.