Question

A small house is in thermal equilibrium at noontime on a cold, winter day. The furnace generates 636 W of heat, while the walls conduct and convect 1,943 W awayfrom the house. How much thermal radiation from the Sun is helping to warm the house?

Answer 1

Since the house is in thermal equilibrium, the amount of heat that enters is equal to the amount of heat that leaves the house.

The amount of heat that enters is equal to the furnace generation plus the heat from the sun, and the amount of heat that leaves is equal to the heat from the wall conduction and convection.

So we have:

`\begin{gathered} \text{Heat in}=\text{ Heat out} \\ 636+\text{sun}=1943 \\ \text{sun}=1943-636 \\ \text{sun}=1307\text{ W} \end{gathered}`

So the thermal radiation from the sun helps with 1307 W.