# A box ,total surface area 2.20m² and a wall thickness 6cm is made of an insulating material.10 W electric heater inside the box maintains the inside temperature at 20°C above the outside temperature. thermal conductivity of the insulating material?

Nov 30, 2015

$\kappa = 0.0136 \text{W/(m.K)}$

#### Explanation:

Thermal conductivity can be thought of as a the flux of heat (energy per unit area per unit time) divided by the temperature gradient(temperature difference per unit length).

The expression is:

$\kappa = \frac{\Delta Q}{\Delta t} . \frac{1}{A} . \frac{x}{T}$

Putting in the values:

$\kappa = 10 \times \frac{1}{2.2} \times \frac{0.06}{20}$

$\therefore \kappa = 0.0316 \text{W/(m.K)}$