$A$ thin paper cup filled with water does not catch fire when placed over a flame. This is because

Heat flows through a rod of length $50 \ cm$ and cross-sectional area $5 \ cm^{2}$. Its ends are maintained at $25 \ ^\circ C$ and $125 \ ^\circ C$ respectively. The thermal conductivity of the material of the rod is $0.092 \ kcal/m \cdot s \cdot ^\circ C$. The temperature gradient of the rod is ....... $^\circ C/cm$.

The difference of temperature in a material can convert heat energy into electrical energy. To harvest the heat energy,the material should have

Write a note on a double-walled flask or a thermos.

Heat is flowing through a conductor of length $l$ from $x = 0$ to $x = l$. If its thermal resistance per unit length is uniform,which of the following graphs correctly represents the variation of temperature $T$ with distance $x$?

$A$ rod of length $50 \, cm$ has one end at $25^oC$ and the other end at $125^oC$. The temperature gradient is ....... $^oC/cm$.