The thermal conductivity of a material in $CGS$ system is $0.4$ . In steady state, the rate of flow of heat $10 cal/sec-cm2$ , then the thermal gradient will be ....... $^oC/cm$

The two ends of a rod of length $L$ and a uniform cross-sectional area $A$ are kept at two temperatures $T_1$ and $T_2 (T_1 > T_2)$. The rate of heat transfer,$\frac{ dQ }{dt}$, through the rod in a steady state is given by

In the following figure, two insulating sheets with thermal resistances $R$ and $3R$ as shown in figure. The temperature $\theta$ is ...... $^oC$

A piece of glass is heated to a high temperature and then allowed to cool. If it cracks, a probable reason for this is the following property of glass

The heat is flowing through two cylindrical rods of same material. The diameters of the rods are in the ratio $1 : 2$ and their lengths are in the ratio $2 : 1$ . If the temperature difference between their ends is the same, the ratio of rate of flow of heat through them will be

$A$ metal rod of length $2$$m$ has cross sectional areas $2A$ and $A$ as shown in figure. The ends are maintained at temperatures $100°C$ and $70°C$ . The temperature at middle point $C$ is...... $^oC$