According to the experiment of Ingen Hausz the relation between the thermal conductivity of a metal rod is $ K$ and the length of the rod whenever the wax melts is

Figure shows three different arrangements of materials $1, 2$ and $3$ to form a wall. Thermal conductivities are $k_1 > k_2 > k_3$ . The left side of the wall is $20\,^oC$ higher than the right side. Temperature difference $\Delta T$ across the material $1$ has following relation in three cases

On a cold morning, a metal surface will feel colder to touch than a wooden surface because 

For the shown figure, calculate the equivalent thermal resistance if the bricks made of the same material of conductivity $K$

Which of the following factors affect the thermal conductivity of a rod?

A metal rod of length $2\, m$ has cross-sectional areas $2A$ and $A$ as shown in the following figure. The two ends are maintained at temperatures $100\,^oC$ and $70\,^oC$. The temperature of middle point $C$ is ........ $^oC$