Gravitational force is required for

A wall has two layer $A$ and $B$ each made of different material, both the layers have the same thickness. The thermal conductivity of the material $A$ is twice that of $B$. Under thermal equilibrium the temperature difference across the wall $B$ is $36^o C$. The temperature difference across the wall $A$ is ....... $^oC$

Two electric lamps $A$ and $B$ radiate the same power. Their filaments have the same dimensions and have emissivities $e_A$ and $e_B$. Their surface temperatures are $T_A$ and $T_B$. The ratio $\frac{{{T_A}}}{{{T_B}}}$ will be equal to :-

The power radiated by a black body is $P$ and it radiates maximum energy around the wavelength $\lambda_0$. If the temperature of the black body is now changed so that it radiates maximum energy around wavelength $\frac{3}{4}\lambda_0$, the power radiated by it will increase by a factor of

A glass flask of volume $1$ litre is fully filled with mercury at $0\,^oC$. Both the flask and mercury are now heated to $100\,^oC$. If the coefficient of volume expansion of mercury is $1.82\times10^{-4}/^oC$, volume coefficient of linear expansion of glass is $10\times10^{-6}/^oC$, the amount of mercury which is spilted out is ............ $\mathrm{ml}$

A body cools from a temperature $60\,^oC$ to $40\,^oC$ in $10$ minutes. The room temperature is $20\,^oC$ . Assume that Newton's law of cooling is applicable. The temperature of the body at the end of next $10$ minutes will be......... $^oC$