Aluminum has only about ________ % of the conductivity of copper.

• A. 90%
• B. 60%
• C. 100%
• D. 30%

Answer: (B)

Conductivity is higher in copper than in aluminum because copper has a lower resistivity. For the same temperature and cross-section, aluminum carries less current than copper. The ratio of their conductivities is about 0.63 (roughly 63%), since ρ_aluminum ≈ 2.65 μΩ·cm and ρ_copper ≈ 1.68 μΩ·cm, and conductivity is the inverse of resistivity. That puts aluminum at about 60% of copper’s conductivity, which matches the given option. In practice, to carry the same current, aluminum needs a larger cross-section than copper, partly offset by its much lighter weight.