On what does the value of the coefficient of linear expansion depend?

$A$ rod is found to be $0.05 \ cm$ longer at $40^{\circ} C$ than it is at $10^{\circ} C$. The length of the rod at $0^{\circ} C$ is (coefficient of linear expansion of the material of the rod $= 1.5 \times 10^{-5} \ {}^{\circ} C^{-1}$) (in $cm$)

Two metal rods $A$ and $B$ each of length $50 \ cm$ and diameter $4.0 \ mm$ are joined together at temperature $30^{\circ} C$. What is the change in length of the combined rod at $230^{\circ} C$ (in $mm$)? [Given linear expansion coefficients of rods $A$ and $B$ are respectively, $2.0 \times 10^{-5} /^{\circ} C$ and $1.0 \times 10^{-5} /^{\circ} C$]

Write the relation between the coefficient of linear expansion $(\alpha_l)$,coefficient of area expansion $(\alpha_A)$,and coefficient of volume expansion $(\alpha_V)$.

$A$ metal rod $2 \,m$ long increases in length by $1.6 \,mm$, when heated from $0^{\circ} C$ to $60^{\circ} C$. The coefficient of linear expansion of the metal rod is:

The gap between any two rails, each of length $l$ laid on a railway track, is equal to $x$ at $27\,^{\circ}C$. When the temperature rises to $40\,^{\circ}C$, the gap closes up. If the coefficient of linear expansion of the material of the rail is $\alpha$, the length $l$ of a rail at $27\,^{\circ}C$ is: