Two rods having same area are used to connect two reservoirs at temperature $100\,^oC$ and $0\,^oC$ as shown. The temperature of junction is $70\,^oC$. If the rods are now interchanged, the temperature of junction will be  ......... $^oC$

Gravitational force is required for

Two circular discs $A$ and $B$ with equal radii are blackend. They are heated to same temperature and are cooled under identical conditions. What inference do you draw from their cooling curves ?

Solar radiation emitted by the sun resembles that emitted by a black body at a temperature of $6000\,K$. Maximum intensity is emitted at wavelength of about $4800{\text{ }}\mathop {\text{A}}\limits^o $. If the sun was cooled down from $6000\,K$ to $3000\,K$, then the peak intensity would occur at a wavelength of ........ $\overset{o}{\mathop{A}}$

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 rigid boxes containing different ideal gases are placed on a table. Box $A$ contains one mole of nitrogen at temperature $T_0$, while box $B$ contains one mole of helium at temperature $(7/3)$ $T_0$. The boxes are then put into thermal contact with each other, and heat flows between them until the gases reach a common final temperature (Ignore the heat capacity of boxes). Then, the final temperature of gases, $T_f$, in terms of $T_0$ is