If the resistivity ρ of a conductor doubles while length and cross-sectional area remain the same, what happens to the resistance?

• A. It stays the same.
• B. It doubles.
• C. It halves.
• D. It quadruples.

Answer: (B)

Resistance is determined by both the material and the shape of the conductor. The formula R = ρL/A shows that, for fixed length L and cross-sectional area A, the resistance changes in direct proportion to the resistivity ρ. If ρ doubles, R doubles as well because the only changing factor is ρ. The geometry stays the same, so there’s no reason for the resistance to stay the same, halve, or quadruple.