Two bodies $P$ and $Q$ have thermal emissivities of $\varepsilon_P$ and $\varepsilon_Q$ respectively. Surface areas of these bodies are same and the total radiant power is also emitted at the same rate. If temperature of $P$ is $\theta_P$ kelvin then temperature of $Q$ i.e. $\theta_Q$ is

A spherical body of emissitivity $e = 0.6$ placed inside a perfect black body is maintained at temperature $T$, then the energy radiated per second will be

Liquid cools from $50^oC$ to $45^oC$ in $5$ minutes and from $5^oC$ to $41.5^oC$ in the next $5$ minutes. The temperature of the surrounding is……… $^oC$

Three rods $A, B,$ and $C$ of thermal conductivities $K, 2K$ and $4K$, cross-sectional areas $A, 2A$ and $2A$ and lengths $2l, l$ and $l$ respectively are connected as shown in the figure. If the ends of the rods are maintained at temperatures $100\,^oC$, $50\,^oC$, and $0\,^oC$ respectively, then the temperature $\theta$ of the junction is

Three rods of same dimensions have thermal conductivities $3K,\,2K$ and $K$. They are arranged as shown with their ends at $100\,^oC$, $50\,^oC$ and $0\,^oC$. Temperature of junction is