Rankers Physics
Topic: Thermal Physics

Consider a compound slab consisting of two different materials having equal thicknesses and thermal conductivities $K$ and $2K$, respectively. The equivalent thermal conductivity of the slab is: (2003)
$sqrt{2} K$
$3 K$
$frac{4}{3} K$
$- K$

Solution:

For compound slab in series, $K_{eq} = frac{l_1 + l_2}{frac{l_1}{K_1} + frac{l_2}{K_2}}$
$K_{eq} = frac{l + l}{frac{l}{K} + frac{l}{2K}} = frac{2l}{frac{3l}{2K}} = frac{4}{3} K$

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