The temperature of the two outer surface of a composite slab, consisting of two materials having coefficients of thermal conductivity K and 2K and thickness x and 4x, respectively are `T_(2)`and `T_(1)(T_(2) gt T_(1))`. The rate of heat transfer through the slab, in a steady state is `((A(T_(2)-T_(1))K)/(x))f`, with f equal to

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`