Five rods of same dimensions are arranged as shown in the figure. They have thermal conductivities K1,K2,K3,K4 and K5. When points A and B are maintained at different temperatures, no heat flows through the central rod if
Two cylindrical rods of lengths l1 and l2, radii r1 and r2 have thermal conductivities k1 and k2 respectively. The ends of the rods are maintained at the same temperature difference. If l1=2l2 and r1=r22, the rates of heat flow in them will be the same if k1k2 is