aluminum and copper wires of equal length are found to have the same resistance. what is the ratio of their radii?
the resistance is directly proportional to the length and resistivity
and inversely proportional to the cross sectional area (the square of the radius)
(Cu radius)² / (Cu resis) = (Al radius)² / (Al resis)
1.6 / (cr)² = 2.7 / (ar)²
1.6 / 2.7 = (cr / ar)²