Consider a compound slab consisting of two different material having equal thickness and thermal conductivities `K` and `2K` respectively. The equivalent thermal conductivity of the slab is

Options

A. `2K`
B. `3K`
C. `(4 K)/(3)`
D. `(2 K)/(3)`

Answer

D

Explanation

(4) `R_(eq) = R_(1) + R_(2)`
`(2L)/(K_(eq) A) = (L)/(KA) + (L)/(2KA)`
`K_(eq) = (2 K)/(3)`