Question

A solid cylindrical rod made from a center cylinder of lead and an outer concentric jacket of copper.Except for its ends,the rod is insulated,so that the loss of heat from the curved surface is negligible.When a temperature difference is maintained between its ends,this rod conducts 1/2 the amount of heat that a copper would conducts.Determine the ration of the radii r1/r2.
Thermal conductivity of copper=390,lead=35

Answer 1

The cross-sectional areas are circular so that ; therefore,