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 $\left.\alpha_{\text {brass }}=1.8 \times 10^{-5} \mathrm{~K}^{-1}\right)$.

If three moles of monoatomic gas $\left(\gamma=\frac{5}{3}\right)$ is mixed with two moles of a diatomic gas…

Two vessels $A$ and $B$ are of the same size and are at same temperature. A contains $1 \mathrm{~g}$ of hydrogen and $B$ contains $1…

$N$ moles of a polyatomic gas $(f=6)$ must be mixed with two moles of a monoatomic gas so that the mixture behaves as a diatomic gas. The…

The parameter that remains the same for molecules of all gases at a given temperature is :

A diatomic gas $(\gamma=1.4)$ does $200 \mathrm{~J}$ of work when it is expanded isobarically. The heat given to the gas in the process is :