A body having a temperature of $27 °\mathrm{C}$ is kept in a room having a temperature of $27 °\mathrm{C}$. Does the body emit any radiation in this case when the room temperature is the same as body temperature?

Two rods A and B of different materials are welded together as shown in figure. Their thermal conductivities are $K_1$ and $K_2$. The thermal conductivity of the composite rod will be

Three rods of identical cross-section and length are made of three different materials of thermal conductivity $K_1, K_2$ and $K_3$, respectively. They are joined together at their ends to make a long rod (see figure). One end of the long rod is maintained at $100°\mathrm{C}$ and the other at $0°\mathrm{C}$ (see figure). If the joints of the rod are at $70°\mathrm{C}$ and $20°\mathrm{C}$ in steady and there is no loss of energy from the surface of the rod, the correct relationship between $K_1\mathit{,}\mathit{ }{K}_{\mathit{2}}$ and $K_3$ is :

Three rods of same dimensions have thermal conductivities $3K, 2K$ and $K$. They are arranged as shown in the figure below. Then in the steady state the temperature of the junction $\text{'}P\text{'}$ is

Temperature difference of ${120}^{o}C$ is maintained between two ends of a uniform rod $AB$ of length $2L.$ Another bent rod $PQ,$ of same cross-section as $AB$ and length $\frac{3L}{2},$ is connected across $AB$ (See figure). In steady state, temperature difference between $P$ and $Q$ will be close to:

Consider a pair of insulating blocks with thermal resistances $R_1$, and $R_2$ as shown in the figure. The temperature $\text{θ}$ at the boundary between the two blocks is

Consider a ball of mass $100 \mathrm{g}$ attached to one end of a spring $\left(k=800 \mathrm{N} {\mathrm{m}}^{-1}\right)$ and immersed in $0.5 \mathrm{kg}$ water. Assume the complete system is in thermal equilibrium. The spring is now stretched to $20 \mathrm{cm}$ and the mass is released so that it vibrates up and down. Estimate the change in temperature of water before the vibrations stop.

(Specific heat of the material of the ball $=400 \mathrm{J} {\mathrm{kg}}^{-1} {\mathrm{K}}^{-1}$ and Specific heat of water $=4200 \mathrm{J} {\mathrm{kg}}^{-1} {\mathrm{K}}^{-1}$)