Six identical conducting rods are joined as shown in figure. Points $A$ and $D$ are maintained at temperature of $200^o C$ and $20^o C$ respectively. The temperature of junction $B$ will be  ....... $^oC$ 

In a composite rod, when two rods of different lengths $l_1$ and $l_2$ and of the same cross-sectional area are joined from end to end then if $K$ is the effective coefficient of thermal conductivity,  the value of $(l_1 + l_2)/K$ is

Two large holes are cut in a metal sheet. If this is heated, distances $AB$ and $BC$, (as shown)

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

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 ........ $K$

Two electric lamps $A$ and $B$ radiate the same power. Their filaments have the same dimensions and have emissivities $e_A$ and $e_B$. Their surface temperatures are $T_A$ and $T_B$. The ratio $\frac{{{T_A}}}{{{T_B}}}$ will be equal to :-