The rate of heat flow through the cross-section of the rod shown in figure is ($T_2 > T_1$ and thermal conductivity of the material of the rod is $K$)
$\frac{{K\pi {r_1}{r_2}\left( {{T_2} - {T_1}} \right)}}{L}$
$\frac{{K\pi {{\left( {{r_1} + {r_2}} \right)}^2}\left( {{T_2} - {T_1}} \right)}}{{4L}}$
$\frac{{K\pi {{\left( {{r_1} + {r_2}} \right)}^2}\left( {{T_2} - {T_1}} \right)}}{{L}}$
$\frac{{K\pi {{\left( {{r_1} + {r_2}} \right)}^2}\left( {{T_2} - {T_1}} \right)}}{{2L}}$
The temperature of the two outer surfaces of a composite slab, consisting of two materials having coefficients of thermal conductivity $K$ and $2K$ and thickness $x$ and $4x$ , respectively are $T_2$ and $T_1$ ($T_2$ > $T_1$). The rate of heat transfer through the slab, in a steady state is $\left( {\frac{{A({T_2} - {T_1})K}}{x}} \right)f$, with $f $ which equal to
Aring consisting of two parts $ADB$ and $ACB$ of same conductivity $k$ carries an amount of heat $H$. The $ADB$ part is now replaced with another metal keeping the temperatures $T_1$ and $T_2$ constant. The heat carried increases to $2H$. What $ACB$ should be the conductivity of the new$ADB$ part? Given $\frac{{ACB}}{{ADB}}= 3$
Three rods $AB, BC$ and $AC$ having thermal resistances of $10\, units, \,10 \,units$ and $20 \,units,$ respectively, are connected as shown in the figure. Ends $A$ and $C$ are maintained at constant temperatures of $100^o C$ and $0^o C,$ respectively. The rate at which the heat is crossing junction $B$ is ........ $ \mathrm{units}$
Surface of the lake is at $2°C$ . Find the temperature of the bottom of the lake..... $^oC$
A thin paper cup filled with water does not catch fire when placed over a flame. This is because