A hollow sphere of inner radius $R$ and outer radius $2R$ is made of a material of thermal conductivity $K$. It is surrounded by another hollow sphere of inner radius $2R$ and outer radius $3R$ made of same material of thermal conductivity $K$. The inside of smaller sphere is maintained at $0^o C$ and the outside of bigger sphere at $100^o C$. The system is in steady state. The temperature of the interface will be ........ $^oC$
$50$
$70$
$75$
$45$
Two rods $A$ and $B$ of different materials are welded together as shown in figure.Their thermal conductivities are $K_1$ and $K_2$ The thermal conductivity of the composite rod will be
The figure shows a system of two concentric spheres of radii $r_1$ and $r_2$ and kept at temperatures $T_1$ and $T_2$, respectively. The radial rate of flow of heat in a substance between the two concentric spheres is proportional to
On which factor does the thermal conductivity depend ?
In the Ingen Hauz’s experiment the wax melts up to lengths $10$ and $25 cm$ on two identical rods of different materials. The ratio of thermal conductivities of the two materials is
Three rods of the same dimensions have thermal conductivities $3k, 2k$ and $k$. They are arranged as shown, with their ends at $100\,^oC, 50\,^oC$ and $0\,^oC$. The temperature of their junction is