Consider the situation as shown in the figure. Find the amount of heat flowing per second through a cross-section of the bent part,if the total heat taken out per second from the end at $200^{\circ} C$ is $150 \ J/s$.

The ratio of thermal conductivity of two rods of different materials is $5 : 4$. If the two rods have the same area of cross-section and the same thermal resistance,what is the ratio of their lengths?

The dimensional formula for thermal resistance is

Two metal plates of equal thickness have thermal conductivities $K_1$ and $K_2$ respectively. They are joined together to form a single plate. The equivalent thermal conductivity of this composite plate is ..........

Three rods $A, B$ and $C$ of thermal conductivities $K, 2K$ and $4K$,cross-sectional areas $A, 2A$ and $2A$ and lengths $2l, l$ and $l$ respectively are connected as shown in the figure. If the ends of the rods are maintained at temperatures $100^{\circ}C, 50^{\circ}C$,and $0^{\circ}C$ respectively,then the temperature $\theta$ of the junction is ......... $^{\circ}C$

Three rods $A, B,$ and $C$ of thermal conductivities $K, 2K$ and $4K$,cross-sectional areas $A, 2A$ and $2A$ and lengths $2l, l$ and $l$ respectively are connected as shown in the figure. If the ends of the rods are maintained at temperatures $100\,^oC$,$50\,^oC$,and $0\,^oC$ respectively,then the temperature $\theta$ of the junction is