A cylinder of radius R, made of a material of thermal conductivity k1, is surrounded by a cylindrical shell of inner radius R and outer radius 2R. The shell is made of a material of thermal conductivity k2. The two ends of the combined system are maintained at two different temperatures. There is no loss of heat across the cylindrial surface and the system is in steady state. The effective thermal conductivity of the system is
1
k1 + k2
2
\(\frac{k_1 k_2}{k_1+k_2}\)
3
\(\frac{k_1+3 k_2}{4}\)
4
\(\frac{3 k_1+k_2}{4}\)
5
Question Not Attempted