Coefficient of linear expansion of brass and steel rods are $\alpha_1$ and $\alpha_2$. Lengths of brass and steel rods are $l_1$ and $l_2$ respectively. If $(l_2 – l_1)$ is maintained same at all temperatures, which one of the following relations holds good ?

Question

( A ) $\alpha_1 l_1 = \alpha_2 l_2$
( B ) $\alpha_1 l_2 = \alpha_2 l_1$
( C ) $\alpha_1 l_2^2 = \alpha_2 l_1^2$
( D ) $\alpha_1^2 l_2= \alpha_2^2 l_1$