A metal rod of Young's modulus $Y$ and coefficient of thermal expansion $\alpha$ is held at its two ends such that its length remains invariant. If its temperature is raised by $t^{\circ} C$, the linear stress developed in it is

Consider two thermometers $T_1$ and $T_2$ of equal length, which can be used to measure temperature over the range $\theta_1$ to $\theta_2$. $T_1$ contains mercury as the thermometric liquid, while $T_2$ contains bromine. The volumes of the two liquids are the same at the temperature $\theta_1$. The volumetric coefficients of expansion of mercury and bromine are $18 \times 10^{-5} \,K ^{-1}$ and $108 \times 10^{-5} \,K ^{-1}$, respectively. The increase in length of each liquid is the same for the same increase in temperature. If the diameters of the capillary tubes of the two thermometers are $d_1$ and $d_2$, respectively. Then, the ratio of $d_1: d_2$ would be closest to

A seconds pendulum clock has a steel wire. The clock shows correct time at $25^{\circ} C$. ………. $s$ time does the clock lose or gain, in one week, when the temperature is increased to $35^{\circ} C$ ? $\left(\alpha_{\text {toel }}=1.2 \times 10^{-5} /{ }^{\circ} C \right)$

$Assertion :$ In pressure-temperature $(P-T)$ phase diagram of water, the slope of the melting curve is found to be negative.
$Reason :$ Ice contracts on melting to water.

If two rods of length $L$ and $2L$ having coefficients of linear expansion $\alpha$ and $2\alpha$ respectively are connected so that total length becomes $3L$, the average coefficient of linear expansion of the composition rod equals: