Give definition, unit and dimensional formula of thermal conductivity.

Four rods of same material and having the same cross section and length have been joined, as shown. The temperature of the junction of four rods will be ............... $^{\circ} C$

The area of the glass of a window of a room is $10\;{m^2}$ and thickness $2mm$. The outer and inner temperature are ${40^o}C$ and ${20^o}C$ respectively. Thermal conductivity of glass in $MKS$ system is $0.2$. The heat flowing in the room per second will be

On which factor does the thermal conductivity depend ?

Which of the following statements is/are $CORRECT$ Correct option are

$(i)$ a body with large reflectivity is a poor emitter

$(ii)$ a brass tumbler feels much colder than a wooden tray on a chilly day

$(iii)$ the earth without its atmosphere would be inhospitably cold

$(iv)$ heating systems based on circulation of steam are more efficient in warming a building than those based on circulation of hot water

$ABCDE$ is a regular pentagon of uniform wire. The rate of heat entering at $A$ and leaving at $C$ is equal. $T_B$ and $T_D$ are temperature of $B$ and $D$ . Find the temperature $T_C$