Question

Consider two copper wires. one has twice the length and twice the cross-sectional area of the other. how do the resistances of these two wires compare?

Answer 1

R = ρ L / A where R is the resistance and ρ the resistivity:

R2 / R1 = (L2 / A2) / (L1 / A1) = L2 * A1 / (L1 * A2)

R2 / R1 = (2 L * A) / (L * 2 A) = 1

Their resistances should be the same.