Calculate the surface temperature of the planet, if the energy radiated by unit area in unit time is $5.67 \times 10^4\,watt$ : (Planet may be assumed to black body)

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 .......... $min$ 

Assuming the sun to be a spherical body of radius $R$ at a temperature of $T$ $K$, evaluate the total radiant power, incident on earth, at a distance $r$ from the sun- (when radius of earth is $r_0$)

Two rods $A$ and $B$ of same cross-sectional are $A$ and length $l$ connected in series between a source $(T_1 = 100^o C)$ and a sink $(T_2 = 0^o C)$ as shown in figure. The rod is laterally insulated The ratio of the thermal resistance of the rod is 

If the temperature of a black body increases from $7\,^oC$ to $287\,^oC$ then the rate of energy radiation increases by

Radiated energy at $TK$ temperature is $E$ for a body of diameter $'d'$. If temperature  becomes $(2T)$ and diameter becomes $\frac{d}{4}$ then radiated energy will be :-