Four identical rods of the same material are joined end to end to form a square. If the temperature difference between the ends of a diagonal is $100^{\circ}C$,then the temperature difference between the ends of the other diagonal will be ........ $^{\circ}C$.

In a composite rod,when two rods of different lengths and of the same area are joined end to end,then if $K$ is the effective coefficient of thermal conductivity,$\frac{{\ell _1} + {\ell _2}}{K}$ is equal to

Two rods of same material have same length and area. The heat $\Delta Q$ flows through them for $12 \, \text{minutes}$ when they are joined in series. If now both the rods are joined in parallel,then the same amount of heat $\Delta Q$ will flow in ........ $\text{minutes}$.

Rods $x$ and $y$ of equal dimensions but of different materials are joined as shown in the figure. Temperatures of end points $A$ and $F$ are maintained at $100^{\circ}C$ and $40^{\circ}C$ respectively. Given the thermal conductivity of rod $x$ is three times that of rod $y$,the temperatures at junction points $B$ and $E$ are (close to):

Six identical rods are arranged as shown in the figure. The temperature of the junction $B$ will be......... $^oC$

Why do people prefer to give a layer of sand or foam insulation on ceilings made of concrete?