Which metals are commonly used as electrical contacts due to their conductivity?

Which metals are commonly used as electrical contacts due to their conductivity?

• A. Gold and silver
• B. Copper and aluminum
• C. Iron and steel
• D. Aluminum and magnesium

Answer: (A)

When selecting metals for electrical contacts, the goal is to maintain a low and stable contact resistance over many mating cycles, even in challenging environments. This means choosing materials with high electrical conductivity and strong resistance to tarnish or corrosion that can raise resistance at the contact interface. Gold and silver fit this requirement well. Silver has the highest electrical conductivity of any metal, so it minimizes resistance and heating at the contact. Gold, while not the absolute top conductor, resists oxidation and corrosion extremely well, so a gold surface remains clean and maintains a low, stable contact resistance over time. This combination—excellent conductivity (in the case of silver) and superior corrosion resistance (in the case of gold)—is why these metals are commonly used for electrical contacts, often as plating or here-and-there choices to ensure reliable performance. Other metals have drawbacks for contact surfaces. Iron and steel conduct poorly compared with copper, and they readily form rust that increases resistance and wear. Aluminum and magnesium form oxide layers that can act as insulators, raising contact resistance and complicating reliable mating. Copper is highly conductive but can still suffer from oxidation in some environments, though it is widely used elsewhere in electrical systems.

When selecting metals for electrical contacts, the goal is to maintain a low and stable contact resistance over many mating cycles, even in challenging environments. This means choosing materials with high electrical conductivity and strong resistance to tarnish or corrosion that can raise resistance at the contact interface.

Gold and silver fit this requirement well. Silver has the highest electrical conductivity of any metal, so it minimizes resistance and heating at the contact. Gold, while not the absolute top conductor, resists oxidation and corrosion extremely well, so a gold surface remains clean and maintains a low, stable contact resistance over time. This combination—excellent conductivity (in the case of silver) and superior corrosion resistance (in the case of gold)—is why these metals are commonly used for electrical contacts, often as plating or here-and-there choices to ensure reliable performance.

Other metals have drawbacks for contact surfaces. Iron and steel conduct poorly compared with copper, and they readily form rust that increases resistance and wear. Aluminum and magnesium form oxide layers that can act as insulators, raising contact resistance and complicating reliable mating. Copper is highly conductive but can still suffer from oxidation in some environments, though it is widely used elsewhere in electrical systems.