QJEEM22Ph186b: JEE Main 2022 Physics - Class 11 JEEM22Ph186b Solution: A unit scale is to be prepared whose length does not change…

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 __________ $$\mathrm{cm}$$. $$({\alpha }_{\text{iron }}=1.2\times {10}^{-5}{\mathrm{K}}^{-1}$$ and $${\alpha }_{\text{brass }}=1.8\times {10}^{-5}{\mathrm{K}}^{-1})$$.