A body cools from $62\,^oC$ to $50\,^oC$ in $10\, minutes$ and to $42\,^oC$ in next $10\, minutes$. The temperature of the surrounding is ……….. $^oC$

It takes $10$ minutes to cool a liquid from $61^{\circ} C$ to $59^{\circ} C$. If room temperature is $30^{\circ} C$ then time taken in cooling from $51^{\circ} C$ to $49^{\circ} C$ is ………. $min$ 

Six wires 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

The surface temperature of the sun which has maximum energy emission at $500\, nm$ is $6000\, K$. The temperature of a star which has maximum energy emission at $400\, nm$ will be …….. $K$

A wall is made up of two layers $A$  and $B.$ The thickness of the two layers is the same, but materials are different. The thermal conductivity of $A$  is double than that of $B.$ In thermal equilibrium the temperature difference between the two ends is $36\,^oC.$ Then the difference of temperature at the two surfaces of  $A$  will be……… $^oC$