JEE Main 2022 · 25 Jul · Shift 1, Physics question 54

A unit scale is to be prepared whose length does not change with temperature and remains 20 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 cm and length of iron will be ______ cm.

($\alpha_{\text{iron}}=1.2\times10^{-5}$ K$^{-1}$ and $\alpha_{\text{brass}}=1.8\times10^{-5}$ K$^{-1}$).