Two rods of different materials having coefficient of linear expansion $\alpha_1$and $\alpha_2$ and  Young's modulii $Y_1$ and $Y_2$ respectively are fixed between two rigid massive walls. The rods are heated such that they undergo the same increase in temperature. There is no bending of rods. If  $\alpha_1:\alpha_2= 2 : 3$, the thermal stress developed in two rods are equal provided $Y_1 : Y_2$ is equal to

If a bimetallic strip is heated, it will

A large steel wheel is to be fitted on to a shaft of the same material. At $27\,^{\circ} C ,$ the outer diameter of the shaft is $8.70\; cm$ and the diameter of the centrall hole in the wheel is $8.69 \;cm$. The shaft is cooled using 'dry ice'. At what temperature (in $^oC$) of the shaft does the wheel slip on the shaft? Assume coefficient of linear expansion of the steel to be constant over the required temperature range: $\alpha_{steel} =1.20 \times 10^{-3} \;K ^{-1}$

A hole is drilled in a metal sheet. At $27^{\circ}\,C$, the diameter of hole is $5\,cm$. When the sheet is heated to $177^{\circ}\,C$, the change in the diameter of hole is $d \times$ $10^{-3}\,cm$. The value of $d$ will be $………..$ if coefficient of linear expansion of the metal is $1.6 \times$ $10^{-5} /{ }^{\circ}\,C$

$Assertion :$ 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.