An iron rod connects the opposite sides of a circular iron ring. If the system is uniformly heated the ring 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