The temperature of the two outer surfaces of a composite slab, consisting of two materials having coefficients of two materials having coefficients of thermal conductivity K and 2K and thickness x and 4x, respectively, are `T_2 and T_1(T_1gtT_1)`. The rate of heat transfer through the slab, in a steady state is `((A(T_2-T_1)K)/2)f`, with f equal to

Options

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

Answer

D

Explanation

`R_(eq)=(x)/(KA)+(4x)/(2KA)=(3x)/(KA)`
`(Q)/(t)=((T_(2)-T_(1)))/(R_(eq))=((T_(2)-T_(1))KA)/(3x)`
Compare this equation with given equation .