Question:
A room has a window fitted with a single $1.0 \mathrm{~m} \times 2.0 \mathrm{~m}$ glass of thickness $2 \mathrm{~mm}$.
(a) Calculate the rate of heat flow through the closed window when the temperature inside the room is $32^{\circ} \mathrm{C}$ and that outside is $40^{\circ} \mathrm{C}$
(b) The glass is now replaced by two glasspanes, each having a thickness of $1 \mathrm{~mm}$ and separated by a distance of $1 \mathrm{~mm}$. Calculate the rate of heat flow under the same conditions of temperature. Thermal conductivity of window glass $=1.0 \mathrm{~J} / \mathrm{m}-\mathrm{s}-{ }^{\circ} \mathrm{C}$ and that of air $=0.025 \mathrm{~J} / \mathrm{m}-\mathrm{s}-{ }^{\circ} \mathrm{C}$
Solution:
