One end of a thermally insulated rod is kept at a temperature $T_1$ and the other at $T_2$. The rod is composed of two sections of lengths $l_1$ and $l_2$ and thermal conductivities $K_1$ and $K_2$ respectively. The temperature at the interface of the two sections is
$\left( {{K_2}{l_2}{T_1} + {K_1}{l_1}{T_2}} \right)/\left( {{K_1}{l_1} + {K_2}{l_2}} \right)$
$\left( {{K_2}{l_1}{T_1} + {K_1}{l_2}{T_2}} \right)/\left( {{K_2}{l_1} + {K_1}{l_2}} \right)$
$\left( {{K_1}{l_2}{T_1} + {K_2}{l_1}{T_2}} \right)/\left( {{K_1}{l_2} + {K_2}{l_1}} \right)$
$\left( {{K_1}{l_1}{T_1} + {K_2}{l_2}{T_2}} \right)/\left( {{K_1}{l_1} + {K_2}{l_2}} \right)$
Two materials having coefficients of thermal conductivity $3K$ and $K$ and thickness $d$ and $3d$, respectively, are joined to form a slab as shown in the figure. The temperatures of the outer surfaces are $\theta_2$ and $\theta_1$ respectively $\left( {\theta _2} > {\theta _1} \right)$ . The temperature at the interface is
Three rods of the same dimension have thermal conductivities $3K$ , $2K$ and $K$ . They are arranged as shown in fig. Given below, with their ends at $100^oC, 50^oC $and $20^oC$. The temperature of their junction is ......... $^oC$
Under steady state, the temperature of a body
In variable state, the rate of flow of heat is controlled by
The rate of heat flow through the cross-section of the rod shown in figure is ($T_2 > T_1$ and thermal conductivity of the material of the rod is $K$)