A partition wall has two layers of different materials A and B in contact with each other. They have the same thickness but the thermal conductivity of layer A is twice that of layer B. At steady state the temperature difference across the layer B is 50 K, then the corresponding difference across the layer A is

Options

A. `50K`
B. `12.5K`
C. `25K`
D. `60K`

Explanation

(c) Let `T` be the junction temperature
Here `K_(A)=2K_(B),T-T_(B)=50K`

At the steady `H_(A)=H_(B)`
`implies (K_(A)A(T_(A)-T))/L=(K_(B)A(T-T_(B)))/L`
`implies 2K_(B)(T_(A)-T)=K_(B)(T-T_(B))`
`impliesT_(A)-T=(T-T_(B))/2`
`=50/2=25K`