# Heat is conducted through a 10 cm thick wall at rate of 30 W/m2. When the temperature difference across wall is 10° C. What is the thermal conductivit

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Heat is conducted through a 10 cm thick wall at rate of 30 W/m2. When the temperature difference across wall is 10° C. What is the thermal conductivity of wall?
1. 0.03 W/mK
2. 0.3 W/mK
3. 3 W/mK
4. 30 W/mK

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Correct Answer - Option 2 : 0.3 W/mK

Concept:

According to Fourier’s Law:

$Q = - kA\frac{{dT}}{{dx}}$

where k = Thermal conductivity, A = cross-section area, $\frac {dT}{dx}$ = Temperature gradient

Calculation:

Given:

dx = 10 cm = 0.1 m, Q = 30 W/m2, dT = 10°C

$Q = -kA\frac{{dT}}{{dx}}$

$\frac{Q}{A} =- k\frac{{dT}}{{dx}}$

$\Rightarrow 30 = k \times \frac{{10}}{{0.1}}$

∴ k = 0.3 W/mK