A metallic scale reads correctly at $\theta =1°\mathrm{C}$. At $\theta °\mathrm{C}$, the correct reading will be

A thin copper wire of length $l$ increases in length by $1\%$ if temperature is changed from ${\theta }_1$ to ${\theta }_2$. What will be the percentage increase of area of a thin copper plate of $2l\times l$ area at the same change of temperature?

A pendulum clock having copper rod keeps correct time at $20°\mathrm{C}$. It gains $15$ seconds per day if cooled to $0°\mathrm{C}$. The coefficient of linear expansion of copper is

Two rods of different materials having coefficients of thermal expansion $\alpha 1$ and $\alpha 2$ are fixed between two rigid and massive walls. The rods are heated to the same temperature. If there is no bending of the rods, the thermal stress developed in them are equal provided

A steel metre scale is to be ruled so that the millimetre intervals are accurate to about $5\times 10-5 \mathrm{mm}$ at a certain temperature. The maximum temperature variation allowed during ruling is (the co-efficient of linear expansion of steel $=10\times 10-6 \mathrm{K}-1)$

When the temperature of a rod increases from $t$ to $t+∆t$, the moment of inertia of the rod increases from $I$ to$I+∆I$. If the coefficient of linear expansion of the rod is $\alpha$, the ratio of $\frac{∆I}{I}$ is