Six wire each of cross-sectional area $A$ and length $l$ are combined as shown in the  figure. The thermal conductivities of copper and iron are $K_1$ and $K_2$ respectively.  The equivalent thermal resistance between points $A$ and $C$ is :-

If the radius and length of a copper rod are both doubled, the rate of flow of heat along the rod increases ....... times

A wall has two layers $A$ and $B$, each made of a different material. Both the layers have the same thickness. The thermal conductivity of the material of $A$ is twice that of $B$. Under thermal equilibrium, the temperature difference across the wall is $36\,^oC$. The temperature difference across the layer $A$ is ......... $^oC$

The temperature $\theta$ at the junction of two insulating sheets, having thermal resistances $R _{1}$ and $R _{2}$ as well as top and bottom temperatures $\theta_{1}$ and $\theta_{2}$ (as shown in figure) is given by

A body of length 1m having cross sectional area $0.75\;m^2$ has heat flow through it at the rate of $ 6000\; Joule/sec$ . Then find the temperature difference if $K = 200\;J{m^{ - 1}}{K^{ - 1}}$ ...... $^oC$

Two identical rods of copper and iron are coated with wax uniformly. When one end of each is kept at temperature of boiling water, the length upto which wax melts are $8.4cm$ and $4.2cm$ respectively. If thermal conductivity of copper is $0.92$ , then thermal conductivity of iron is