Which of the following materials would have the highest resistivity value?

The material with the highest resistivity value is Zirconium, indicated by its low IACS (International Annealed Copper Standard) rating of 3.4 percent. IACS ratings measure the electrical conductivity of metals relative to copper, the standard reference material, where a lower percentage signifies a higher resistivity.

Since resistivity and conductivity are inversely related, materials with lower IACS ratings demonstrate higher resistivity. Zirconium’s low IACS rating reflects its characteristics as a poor conductor of electricity compared to the other materials listed.

In contrast, aluminum and magnesium, while not as conductive as copper, possess significantly higher IACS ratings, indicating they have lower resistivity values than Zirconium. Cast steel, with an even lower conductivity, has the highest IACS rating among the other options but is still far below that of Zirconium. This relationship highlights why Zirconium emerges as the material with the highest resistivity in this context.