Which of the following is a common material used for electrical conductors?

Copper-clad aluminum is widely used for electrical conductors due to its combination of properties. It offers the conductivity characteristics of copper while being lighter and often less expensive due to the aluminum core. This material is particularly advantageous in applications where weight is a consideration, such as in overhead power lines or certain types of electrical wiring.

Copper is traditionally known for its excellent electrical conductivity, and the copper cladding ensures that the conductor maintains a high level of performance while reducing overall material costs. This makes copper-clad aluminum a practical choice in both residential and industrial electrical applications. The core aluminum reduces weight, making it easier to handle and install, contributing to its popularity in various electrical installations.

The other options listed, while they may have electrical properties, do not serve the same primary function as conductors. Plastic and rubber, for example, are typically used as insulators, preventing electrical flow and protecting the conductor from external elements. Silicon, while it is a semiconductor and plays a critical role in electronics, is not a traditional conductor like copper or aluminum.