Physics

Problem

A refrigerator wall of area

0.50\,\text{m}^2

must limit heat leakage to

30\,\text{W}

when the temperature difference across it is

20\,\text{K}

. If an insulating material of thermal conductivity

0.04\,\text{W m}^{-1}\,\text{K}^{-1}

is used, the minimum thickness required is closest to a)

0.7\,\text{cm}

3.9\,\text{cm}

1.3\,\text{cm}

2.6\,\text{cm}