Q154 / 160 · WBJEE 2011 · Physics

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

  • A
    0.11
  • Correct answer
    B
    0.13
  • C
    0.15
  • D
    1.2

Solution

Hints: \(\frac{\mathrm{dQ}}{\mathrm{dt}}=\frac{\mathrm{KA} \Delta \mathrm{T}}{\mathrm{x}}\) \(\begin{aligned} & \frac{1.56 \times 10^5}{3600}=\frac{\mathrm{K} \times 2 \times 20}{12 \times 10^{-2}} \\ & \mathrm{~K}=\frac{1.56 \times 10^5 \times 12 \times 10^{-2}}{3600 \times 2 \times 20} \\ & =\frac{1.56}{12}=0.13 \end{aligned}\)

Hence, the correct answer is option: 'B'.

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