Which of the following materials is a common ground for electrical systems?

Copper is widely recognized as a common ground material for electrical systems due to its excellent conductivity. This high conductivity allows for efficient distribution of electrical currents, minimizing resistance and heat generation. As a result, copper is often employed in grounding systems to ensure safety by facilitating the effective diversion of fault currents or lightning strikes into the earth.

Additionally, copper's durability and resistance to corrosion contribute to its reliability as a grounding material over time. This makes it ideal for use in various electrical systems, ensuring that grounding integrity is maintained under a wide range of environmental conditions.

In contrast, materials like plastic and rubber are insulators, which do not provide a conductive path required for grounding. Wood, while a natural material, also lacks the necessary conductivity to serve effectively as a ground. Each of these alternatives would not meet the functionality and safety standards required for grounding systems in electrical applications.