Two spheres of different materials one with double the radius and one-fourth wall thickness of the
Channel: Doubtnut
Date: 2020-07-26

Two spheres of different materials one with double the radius and one-fourth wall thickness of the other are filled with ice. If the time taken for complete melting of ice in the larger sphere is `25` minutes and for smaller one is `16` minutes, the ratio of thermal conductivities of the materials of larger sphere to that of smaller sphere is: