Two rods, one made of copper and the other steel of the same length and cross-sectional area are joined together. The thermal conductivity of copper is $385 \,Js ^{-1} m ^{-1} K ^{-1}$ and steel is $50 \,Js ^{-1} m ^{-1} K ^{-1}$. If the copper end is held at $100^{\circ} C$ and the steel end is held at $0^{\circ} C$, the junction temperature is ........... $C$ (Assuming no other heat losses)
$12$
$50$
$73$
$88$
The quantity of heat which crosses unit area of a metal plate during conduction depends upon
$Assertion :$ A brass tumbler feels much colder than a wooden tray on a chilly day.
$Reason :$ The thermal conductivity of brass is more than the thermal conductivity of wood.
Two spheres of different materials one with double the radius and one-fourth wall thickness of the other, are filled with ice. If the time taken for complete melting ice in the large radius one is $25$ minutes and that for smaller one is $16$ minutes, the ratio of thermal conductivities of the materials of larger sphere to the smaller sphere is
A slab consists of two parallel layers of two different materials of same thickness having thermal conductivities $K_1$ and $K_2$ . The equivalent conductivity of the combination is
Five identical rods are joined as shown in figure. Point $A$ and $C$ are maintained at temperature $120^o C$ and $20^o C$ respectively. The temperature of junction $B$ will be....... $^oC$