Coefficient of linear expansion of brass and steel rods are α1 and α2. Lengths of brass and steel rods are l1 and l2 respectively. If (l2 - l1) is maintained same at all temperatures, which one of the following relations holds good?
1
\({\alpha _1}^2{l_2} = {\alpha _2}^2{l}\)
2
\({\alpha _1}{l_2}^2 = {\alpha _2}{l_1}^2\)
3
\({\alpha _1}^2{l_2} = {\alpha _2}^2{l_1}\)
4
\({\alpha _1}{l_1} = {\alpha _2}{l_2}\)