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 :
Answer & explanation
Correct answer: option 2
R = \(\frac{l}{KA}\)
\(\frac{1}{R}\) = \(\frac{1}{R_1}\) + \(\frac{1}{R_2}\)
\(\frac{1}{\frac{l}{K_{eff}A}}\) = \(\frac{1}{\frac{l}{K_1A/2}}\) + \(\frac{1}{\frac{l}{K_2A/2}}\)
On solving ,
K = \(\frac{K_1 +K_2}{2}\)