A slab consists of two layers of different materials of the same thickness and having thermal conductivities `K_(1)` and `K_(2)`. The equivalent thermal conductivity of the slab is

Options

A. `(2k_31K_2)/(K_1+k_2)`
B. `sqrt(K_1K_2)`
C. `(K_1K_2)/(K_1+K_2)`
D. `K_1+ K_2`

Answer

A

Explanation

In series combination , `(t)/(K_(1)) + (t)/(K_(2)) = (2t)/(K)`
`implies (1)/(K_(1)) + (1)/(K_(2)) = (2)/(K) implies k = (2K_(1) K_(2))/(K_(1) + K_(2))`