Two metal rods $P$ and $Q$ have the same length and the same temperature difference between their ends. Their thermal conductivities are $K_1$ and $K_2$,and their cross-sectional areas are $A_1$ and $A_2$ respectively. If the rate of flow of heat through rod $Q$ is three times that in rod $P$,then:

The temperature drop through each layer of a two-layer furnace wall is shown in the figure. Assume that the external temperatures $T_1$ and $T_3$ are maintained constant and $T_1 > T_3$. If the thicknesses of the layers $x_1$ and $x_2$ are the same,which of the following statements is correct?

Two rectangular blocks $A$ and $B$ of different metals have the same length and the same area of cross-section. They are kept in such a way that their cross-sectional areas touch each other. The temperature at one end of $A$ is $100^{\circ}C$ and that of $B$ at the other end is $0^{\circ}C$. If the ratio of their thermal conductivities is $1 : 3$,then under steady state,the temperature of the junction in contact will be ........ $^{\circ}C$.

For a spherical shell with inner and outer radii $r_1$ and $r_2$ respectively,the formula for the heat flow rate is = ......... where $T_1$ and $T_2$ are the temperatures of the inner and outer surfaces of the shell $(T_1 > T_2)$. The thermal conductivity of the material of the shell is $k$.

For cooking the food,which of the following type of utensil is most suitable?

Heat current is maximum in which of the following (rods are of identical dimension)?