A builder compares four walls for a new house.
Each wall has the same area. The temperature difference between the inside and the outside of each wall is the same.
The Table shows information about the walls.
Table
| Wall | Material | Thickness in cm\text{cm}cm | Thermal conductivity in W/m K\text{W/m K}W/m K |
|---|---|---|---|
| P | brick | 10 | 0.70 |
| Q | brick | 20 | 0.70 |
| R | concrete | 20 | 1.40 |
| S | foam block | 20 | 0.04 |
Give the wall that would cause the house to cool most slowly.
Give a reason for your answer.
Use walls P and Q to explain how the thickness of a wall affects the rate of cooling of a house.
The builder says:
'Wall R would keep the house warmer than wall Q because concrete is a better conductor than brick.'
Explain why the builder is wrong.