The temperature of the two outer surfaces of a composite slab, consisting of two materials having coefficients of thermal conductivity K and 2K and thickness x and 4x respectively. Temperatures on the opposite faces of composite slab are `T_(1) and T_(2)` where `T_(2)gtT_(1)`, as shown in fig. what is the rate of flow of heat through the slab in a steady state?

Options

A. `1`
B. `1//2`
C. `2//3`
D. `1//3`

Answer

D

Explanation

`overset(**)(Q)=(T_(2) - T_(1))/((x)/(KA) + (4x)/(2KA)) = (KA(T_(2)-T_(1)))/(3x) = [(KA(T_(2)-T_(1)))/(x)]f`
then f = `1//3`