$A$ cylindrical metal rod of length $L_0$ is shaped into a ring with a small gap as shown. On heating the system,

Three rods of equal lengths are joined to form an equilateral triangle $ABC$. $D$ is the mid-point of $AB$. The coefficient of linear expansion is $\alpha_1$ for the material of rod $AB$ and $\alpha_2$ for the material of rods $AC$ and $BC$. If the distance $DC$ remains constant for small changes in temperature, then:

An aluminium and steel rod having same lengths and cross-sections are joined to make a total length of $120 \ cm$ at $30^{\circ} C$. The coefficients of linear expansion of aluminium and steel are $24 \times 10^{-6} /{ }^{\circ} C$ and $1.2 \times 10^{-5} /{ }^{\circ} C$, respectively. The length of this composite rod when its temperature is raised to $100^{\circ} C$, is . . . . . . $cm$. (in $cm$)

Thermal expansion of a solid is due to the

When a bimetallic strip is heated, it . . . . . . .

The density of a substance at $0 \, ^\circ C$ is $10 \, g/cm^3$ and at $100 \, ^\circ C$ is $9.7 \, g/cm^3$. The coefficient of linear expansion of the substance is ..... $^\circ C^{-1}$.