Heat is flowing through two cylindrical rods of the same material. The diameters of the rods are in the ratio $1:2$ and their lengths are in the ratio $2:1$. If the temperature difference between their ends is the same,then the ratio of the amounts of heat conducted through per unit time will be

If two metallic plates of equal thicknesses and thermal conductivities $K_1$ and $K_2$ are put together face to face and a common plate is constructed,then the equivalent thermal conductivity of this plate will be

$A$ cylindrical copper rod of length $2 \,m$ and cross-sectional area $2 \,cm^2$ is insulated at its curved surface. One end of the rod is maintained in a steam chamber at $100^{\circ} C$ and the other is maintained in ice at $0^{\circ} C$. The thermal conductivity of copper is $386 \,Js^{-1} \,m^{-1} {}^{\circ} C^{-1}$. Find the temperature at a point which is at a distance of $120 \,cm$ from the colder end. (in $^{\circ} C$)

In an $Ingen-Hauz$ experiment,the wax melts on two rods up to lengths of $10 \ cm$ and $25 \ cm$ respectively. If the two rods are made of different materials,what is the ratio of their thermal conductivities?

In the Ingen-Hauz's experiment,the wax melts up to lengths $10 \ cm$ and $25 \ cm$ on two identical rods of different materials. The ratio of thermal conductivities of the two materials is:

In the figure shown,$AB$ is a rod of length $30 \ cm$,area of cross-section $1 \ cm^2$ and thermal conductivity $336 \ SI$ units. The ends $A$ and $B$ are at constant temperatures $20^{\circ} C$ and $40^{\circ} C$ respectively. $A$ point $C$ of the rod is connected to ice at $0^{\circ} C$ in a thermally insulated box $D$ through a highly conducting wire of negligible heat capacity. The rate at which ice melts in the box is $\left(L_{ice}=80 \ cal \ g^{-1}\right)$.