A wall of uniform thickness is made by placing two materials side by side so that…

PHYSICS · Single correct · A Level · Physics · Further mechanics and thermal physics · Further mechanics and thermal physics

Problem

A wall of uniform thickness

1\,\text{cm}

is made by placing two materials side by side so that heat can flow through them in parallel. Material A covers

0.40\,\text{m}^2

of the total

1\,\text{m}^2

area and has thermal conductivity

0.2\,\text{W m}^{-1}\text{K}^{-1}

. Material B covers the remaining area and has thermal conductivity

0.8\,\text{W m}^{-1}\text{K}^{-1}

. The effective thermal conductivity of the wall is (a)

0.50\,\text{W m}^{-1}\text{K}^{-1}

(b)

0.56\,\text{W m}^{-1}\text{K}^{-1}

(c)

0.36\,\text{W m}^{-1}\text{K}^{-1}

(d)

0.44\,\text{W m}^{-1}\text{K}^{-1}