Statement $A$: Convection involves flow of matter within a fluid due to unequal temperatures of its parts.
Statement $B$: $A$ hot bar placed under a running tap water loses heat due to the effect of convection within water.
Statement $C$: Heat transfer always involves a temperature difference between two systems.

$A$ 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?

$A$ 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 $T_{1} / T_{2}$?

The power radiated by a black body is $P$ and it radiates maximum energy around the wavelength $\lambda_0$. Now the temperature of the black body is changed so that it radiates maximum energy around wavelength $\left(\frac{\lambda_0}{2}\right)$. The power radiated by it will now increase by a factor of

In a closed room,heat transfer takes place by

In Column-$I$,system surroundings and in Column-$II$ modes of heat transfer are given below. Match the following:

Column-$I$	Column-$II$
$(a)$ Cup of hot tea in room	$(i)$ Forced convection
$(b)$ Substance kept near fire	$(ii)$ Natural convection
	$(iii)$ Conduction
	$(iv)$ Radiation