Question

$1.56\times 10^{5}\, J$ of heat is conducted through $2\,m^{2}$ wall of $12\,cm$ thick in $1\,h$ . Temperature difference between the two sides of the wall is $20^{\circ} C$ . The thermal conductivity of the material of the wall is (in $W\, m^{- 1}\,K^{- 1}$ ) $\alpha $ . Write the value of $100\alpha $ .

Answer 1

Rate of heat flow, $\quad \frac{ d Q}{ d t}=\frac{K A \Delta T}{x}$
$\Rightarrow \frac{1.56 \times 10^{5}}{3600}=\frac{K \times 2 \times 20}{12 \times 10^{-2}} $
$\Rightarrow K=\frac{1.56 \times 10^{5} \times 12 \times 10^{-2}}{3600 \times 2 \times 20} $
$=\frac{1.56}{12}=0.13$