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 $\left(l_2-l_1\right)$ is maintained same at all temperatures, which one of the following relations holds good?

Two rods $A$ and $B$ of identical dimensions are at temperature $30\,^oC$. If a heated upto $180\,^oC$ and $B$ upto $T\,^oC$, then the new lengths are the same. If the ratio of the coefficients of linear expansion of $A$ and $B$ is $4:3$, then the value of $T$ is........$^oC$

A copper rod of length $l_1$ and an iron rod of length $l_2$ are always maintained at the same common temperature $T$. If the difference $(l_2 -l_1)$ is $15\,cm$ and is independent of the value of $T,$ the $l_1$ and $l_2$ have the values (given the linear coefficient of expansion for copper and iron are $2.0 \times 10^{-6}\,C^{-1}$ and $1.0\times10^{-6}\,C^{ -1}$  respectively)

A steel rod with ${y}=2.0 \times 10^{11} \,{Nm}^{-2}$ and $\alpha=10^{-5}{ }^{\circ} {C}^{-1}$ of length $4\, {m}$ and area of cross-section $10\, {cm}^{2}$ is heated from $0^{\circ} {C}$ to $400^{\circ} {C}$ without being allowed to extend. The tension produced in the rod is ${x} \times 10^{5} \, {N}$ where the value of ${x}$ is ....... .

If the volume of a block of metal changes by $0.12 \%$ when it is heated thrugh $20^oC$, the coefficient of linear expansion (in $^oC^{-1}$) of the metal is

The value of coefficient of volume expansion of glycerin is $5 \times 10^{-4}k^{-1} .$ The fractional change in the density of glycerin for a rise of $40^o C$ in its temperature, is