Heat And Thermodynamics

A unit scale is to be prepared whose length does not change with temperature and remains \(20 \mathrm{~cm}\), using a bimetallic strip made of brass and iron each of different length. The length of both components would change in such a way that difference between their lengths remains constant. If length of brass is \(40 \mathrm{~cm}\) and length of iron will be __________ \(\mathrm{cm}\). \(\left(\alpha_{\text {iron }}=1.2 \times 10^{-5} \mathrm{~K}^{-1}\right.\) and \(\left.\alpha_{\text {brass }}=1.8 \times 10^{-5} \mathrm{~K}^{-1}\right)\).