
I.e. the temperature gradient is a constant and the temperature drops linearly with distance.
Temperature at midpoint of $\mathrm{AB}=\frac{T_{A}+T_{B}}{2}=50^{\circ} \mathrm{C}=T_{P}$
Temperature at midpoint of $\mathrm{CD}=\frac{T_{C+T_{D}}}{2}=45^{\circ} C=T_{Q}$
since temperature at $P$ is more than that at $Q,$ heat flows from $P$ to $Q .$
$(i)$ a body with large reflectivity is a poor emitter
$(ii)$ a brass tumbler feels much colder than a wooden tray on a chilly day
$(iii)$ the earth without its atmosphere would be inhospitably cold
$(iv)$ heating systems based on circulation of steam are more efficient in warming a building than those based on circulation of hot water
