Six identical conducting rods are joined as shown in figure. Points $A$ and $D$ are maintained at temperatures $200\,^oC$ and $20\,^oC$, respectively. the temperature of junction $B$ will be......... $^oC$
$120$
$100$
$140$
$80$
Heat is conducted across a composite block of two slabs of thickness $d$ and $2d$. Their thermal conductivities are $2k$ and $k$ respectively. All the heat entering the face $AB$ leaves from the face $CD$. The temperature in $^o C$ of the junction $EF$ of the two slabs is :
The radiant energy from sun incident normally at the surface of earth is $20\, kcal/m^2-min$. What would have been the radiant energy incident normally on the earth if the sun had a temperature twice of the present one ......... $kcal/m^2-min$
$Assertion :$ Bodies radiate heat at all temperatures.
$Reason :$ Rate of radiation of heat is proportional to the fourth power of absolute temperature.
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
Six identical conducting rods are joined as shown in figure. Points $A$ and $D$ are maintained at temperature of $200^o C$ and $20^o C$ respectively. The temperature of junction $B$ will be ....... $^oC$