Materials made of copper or silver are considered:

• A. Insulators
• B. Semiconductors
• C. Dielectrics
• D. Conductors

Answer: (D)

Copper and silver are metals with many free electrons that respond to an electric field, so they conduct electricity readily. This free-electron behavior gives metals very low resistivity, which is the defining trait of conductors. Insulators block current because their electrons are tightly bound, dielectrics are insulating materials used to store energy and aren’t good conductors at normal voltages, and semiconductors have conductivity between conductors and insulators and can be tuned by doping and fields. Because copper and silver enable easy current flow, they are classified as conductors. Copper is widely used for wiring due to its good conductivity and practical cost, while silver is an even better conductor but is more expensive.