Canadian Welding Bureau (CWB) Level 3 Practice Exam

Electrical resistivity is an intrinsic property that tells you how easily a material allows electric current to flow. Lower resistivity means better conductivity; higher resistivity means more opposition to current.

Between aluminum and carbon steel, carbon steel has the higher resistivity. At room temperature, aluminum is about 2.8×10^-8 Ω·m, while carbon steel is around 1×10^-7 Ω·m, roughly four times higher. The higher resistivity in carbon steel comes from its iron-based lattice plus carbon and other alloying elements that create more scattering centers for electrons, impeding flow more than in aluminum. Copper, by contrast, has even lower resistivity, which is why it’s such a preferred conductor. Iron’s resistivity sits between aluminum and carbon steel, but the specific comparison here shows carbon steel as the higher resistivity material.