Conductor design principle: Does increasing a conductor’s cross-sectional area reduce its resistance and therefore affect how much it opposes current?

Introduction / Context:
Wire sizing impacts voltage drop, heating, and efficiency. Understanding how geometry influences resistance helps in selecting conductors for power distribution and signal integrity.

Given Data / Assumptions:

• Uniform conductor of length L and cross-sectional area A.
• Material has resistivity ρ at the operating temperature.
• Direct current conditions (but the geometric relation holds for AC resistance ignoring skin effect).

Concept / Approach:
The basic relationship for resistance is R = ρ * L / A. For fixed material (ρ constant) and length L, R is inversely proportional to area. Doubling area halves resistance, which reduces voltage drop and I^2R heating for a given current.

Step-by-Step Solution:

Verification / Alternative check:
Compare AWG tables: lower AWG numbers (thicker wires, larger area) exhibit lower resistance per unit length, confirming the formula.

Why Other Options Are Wrong:

• “Only length matters” (option b) contradicts R ∝ L / A.
• “Only resistivity matters” (option c) ignores geometry.
• “Increasing area increases resistance” (option d) reverses the proportionality.

Common Pitfalls:
Overlooking temperature dependence of ρ and ignoring skin effect at high frequencies, which effectively reduces the conductive area.

Final Answer:
Applies — larger cross-section reduces resistance (R ∝ 1/A).