Question

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

• A. $0.11$
• B. $0.13$
• C. $0.15$
• D. $1.2$

Answer 1

Answer: (B)

Given that $1.56\times 10^{5}J$ of heat is conducted through a $2m^2$ wall having a thickness of $12cm$ in a time interval of $1h$.
Hence, we have $\frac{dQ}{dt}=\frac{KA\Delta T}{x}$
Thus, we get $\frac{1.56\times 10^5}{1\times 60\times 60}$
$=\frac{K\times 2\times 20}{12\times 10^{-2}}$
So, $K=\frac{1.56\times 10^5\times 12\times 10^{-2}}{1\times 60\times 60\times 2\times 20}$
$=\frac{1.56}{12}=0.13$