Two metal plates $P$ and $Q$ of the same material are arranged as shown in the figure. If both the plates are uniformly heated through the same range of temperature,then

The area of a circular copper coin increases by $0.4 \%$ when its temperature is raised by $100^{\circ} C$. The coefficient of linear expansion of the coin is:

$A$ $50 \ cm$ iron rod is connected to a $100 \ cm$ aluminum rod at $20^{\circ}C$. If $\alpha_{Fe} = 12 \times 10^{-6} {^{\circ}C}^{-1}$ and $\alpha_{Al} = 24 \times 10^{-6} {^{\circ}C}^{-1}$,what is the effective coefficient of linear expansion of the system?

The volume of a metal sphere increases by $0.33 \%$ when its temperature is raised by $50^{\circ} C$. The coefficient of linear expansion of the metal is

As shown in the figure,an equilateral triangle $ABC$ is formed by joining three rods of equal lengths $l$. $D$ is the midpoint of $AB$. The coefficient of linear expansion of the material of rod $AB$ is $\alpha_1$ and that of rods $AC$ and $BC$ is $\alpha_2$. If the length $DC$ remains constant for small changes in temperature,then:

$A$ metallic tape gives the correct value at $25^{\circ} C$. $A$ piece of wood is being measured by this metallic tape at $10^{\circ} C$. If the reading is $30 \, cm$ on the tape, the real length of the wooden piece must be .......... $cm$.