$A$ rod of length $L$ and uniform cross-sectional area has varying thermal conductivity which changes linearly from $2K$ at end $A$ to $K$ at the other end $B$. The ends $A$ and $B$ of the rod are maintained at constant temperatures $100^oC$ and $0^oC$, respectively. At steady state, the graph of temperature $T = T(x)$, where $x$ is the distance from end $A$, will be:

Three identical rods $AB$,$CD$ and $PQ$ are joined as shown. $P$ and $Q$ are midpoints of $AB$ and $CD$ respectively. Ends $A, B, C$ and $D$ are maintained at $0^{\circ} C, 100^{\circ} C, 30^{\circ} C$ and $60^{\circ} C$ respectively. The direction of heat flow in $PQ$ is

$A$ wall with a cavity consists of two layers of brick separated by a layer of air. All three layers have the same thickness,and the thermal conductivity of the brick is much greater than that of air. The left layer is at a higher temperature than the right layer,and a steady-state condition exists. Which of the following graphs correctly predicts the variation of temperature $T$ with distance $d$ inside the cavity?

One end of a uniform metal rod of length $100 \, cm$ is placed in ice and the other end is placed in boiling water. A point of the rod which is at a distance of $60 \, cm$ from the ice end is maintained at a constant temperature of $325^{\circ} C$. If $2 \, g$ of water is converted into steam per second, the mass of ice melted per second in steady state is (Latent heat of steam $= 6.75$ times latent heat of fusion of ice). (in $g$)

Two rods (one semi-circular and other straight) of the same material and of the same cross-sectional area are joined as shown in the figure. The points $A$ and $B$ are maintained at different temperatures. The ratio of the heat transferred through a cross-section of the semi-circular rod to the heat transferred through a cross-section of the straight rod in a given time is

Statement $A$: Convection involves flow of matter within a fluid due to unequal temperatures of its parts.
Statement $B$: $A$ hot bar placed under a running tap water loses heat due to the effect of convection within water.
Statement $C$: Heat transfer always involves a temperature difference between two systems.