Two rods A and B of different materials are welded together as shown in figure. Their thermal conductivities are `K_(1)` and `K_(2)`. The thermal conductivity of the composite rod will be

Options

A. `2(k_(1)+k_(2))`
B. `(3)/(2)(k_(1)+k_(2))`
C. `(k_(1)+k_(2))`
D. `(1)/(2)(k_(1)+k_(2))`

Answer

D

Explanation

As we use
`k_(eq) =(k_(1)A_(1)+k_(2)A_(2))/(A_(1)+A_(2))`
`rArr`` k_(eq) =(k_(1)A+k_(2)A)/(A+A) =(k_(1)+k_(2))/(2)`