Two rods A and B of different materials are welded together as shown in figure. Their thermal conductivities are K1 and K2. The thermal conductivity of the composite rod will be
1
2(K1 + K2)
2
\(\frac{K_{1}+K_{2}}{2}\)
3
\(\frac{3\left(K_{1}+K_{2}\right)}{2}\)
4
K1 + K2