Two slabs `A` and `B` of equal surface area are placed one over the other such that their surfaces are completely in contact The thickness and coefficient of thermal conductivities of slab `A` is twice that `B` The first surface of slab `A` is maintained at `100^(@) C` while the second surface of slab `B` is maintained at `25^(@)C` The temperature at the contact of their surfaces is .

Options

A. `15^(@)C`
B. `62.5^(@)C`
C. `55^(@)C`
D. `85^(@)C`

Answer

B

Explanation

`((Q)/(t))_(A)=((Q)/(t))_(B)rArr(2K(100-theta))/(2l)=(K(theta-25))/(l)`