$A$ wall with a cavity consists of two layers of brick separated by a layer of air. All three layers have the same thickness,and the thermal conductivity of the brick is much greater than that of air. The left layer is at a higher temperature than the right layer,and a steady-state condition exists. Which of the following graphs correctly predicts the variation of temperature $T$ with distance $d$ inside the cavity?

The only possibility of heat flow in a thermos flask is through its cork,which is $75 \ cm^2$ in area and $5 \ cm$ thick. Its thermal conductivity is $0.0075 \ cal/(cm \cdot s \cdot ^\circ C)$. The outside temperature is $40^\circ C$ and the latent heat of fusion of ice is $80 \ cal/g$. The time taken by $500 \ g$ of ice at $0^\circ C$ in the flask to melt into water at $0^\circ C$ is ....... $hr$.

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

Three discs $x, y$ and $z$ having radii $2 \ m, 2 \ m$ and $6 \ m$ respectively are coated on their outer surfaces. If the wavelengths corresponding to the maximum power radiated by them are $3 \ \mu m, 4 \ \mu m$ and $5 \ \mu m$ respectively,then which of the following is true regarding the power radiated $(P)$?

$A$ heated body maintained at $T \ K$ emits thermal radiation of total energy $E$ with a maximum intensity at frequency $v$. The emissivity of the material is $0.5$. If the temperature of the body is increased and maintained at temperature $3T \ K$,then:
$(i)$ The maximum intensity of the emitted radiation will occur at frequency $v/3$.
$(ii)$ The maximum intensity of the emitted radiation will occur at frequency $3v$.
$(iii)$ The total energy of emitted radiation will become $81E$.
$(iv)$ The total energy of emitted radiation will become $27E$.

$A$ thin piece of thermal conductor of constant thermal conductivity,insulated on the lateral sides,connects two reservoirs which are maintained at temperatures $T_{1}$ and $T_{2}$ as shown in the figure. Assuming that the system is in a steady state,which of the following plots best represents the dependence of the rate of change of entropy on the ratio $T_{1} / T_{2}$?