Physics - Heat & Thermo Question with Solution | TestHub

An electric heater is used in a room of total wall area $50{\mathrm{m}}^2$ to maintain a constant temperature of $15^{\circ }\mathrm{C}$ inside when the outside temperature is $-10^{\circ }\mathrm{C}$. The walls have two different layers. The inner layer is of cement of thickness 2 cm , while the outer layer is of brick of thickness 10 cm . Assume that there is no loss of heat from the floor and the ceiling. Take the thermal conductivities of cement and brick to be $0.2\mathrm{W}/{\mathrm{m}}^{\circ }\mathrm{C}$ and $0.5\mathrm{W}/{\mathrm{m}}^{\circ }\mathrm{C}$, respectively. If another identical heater is now switched on, along with the old heater, find the steady state temperature (in ${}^{\circ }\mathrm{C}$ ) inside the room, after a long time, if the outside temperature has now dropped to $-15^{\circ }\mathrm{C}$. If your answer is Z then find (Z-30 )?