For heat to flow from one end to the other in a solid,it is necessary to have:

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

The temperature gradient in a rod of length $75 \ cm$ is $40^{\circ} C/m$. If the temperature of the cooler end of the rod is $10^{\circ} C$,then the temperature of the hotter end is: (in $^{\circ} C$)

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 $x$?

The heat is flowing through a rod of length $50 \ cm$ and area of cross-section $5 \ cm^2$. Its ends are respectively at $25^\circ C$ and $125^\circ C$. The coefficient of thermal conductivity of the material of the rod is $0.092 \ kcal/m \cdot s \cdot ^\circ C$. The temperature gradient in the rod is

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