TS EAMCET 06 May 2019 Shift 1 Solved Paper

Two thin metallic spherical shells of radii 20 cm and 30 cm. respectively are placed with their centres coinciding. A material of thermal conductivity α is filled in the space between the shells. The inner shell is maintained at 300 K and the outer shell at 310 K. If the rate at which heat flows radially through the material is 40 W, find the value of α (in units of J s−1m−1K−1):