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 ?
(1) ``\alpha_1`` ``l_2`` = ``\alpha_2````l_1``
(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``