Thermal Properties Of Matter

When two charges and are situated in vacuum at a distance metre, then the electric potential energy of the system is joule
In order that system be in equilibrium, the potential energy of the system should be zero.

A black body is an object that absorbs all electromagnetic radiation that falls on to it. No radiation passes through it and none is reflected. Hence, its emissive power is unity

Heat required to raise the temperature of of water from to , is equivalent to sum of heat required to condense the steam.
Heat required to raise the temperature of water by is
(i)
where, is specific heat of water and the mass.
Heat required to condense steam
(ii)
Equating Eqs. (i) and (ii), we get

Given

From Stefan's law of radiation, the total radiant energy emitted per second per unit surface area of a black body is proportional to the fourth power of the absolute temperature of the body.
Therefore, where is Stefan's constant.
Given,


Hence, total energy radiated by star is sixteen times as that of the sun.

Wien's displacement law

where b = Wien's constant

Thus, is inversely proportional to absolute temperature (T)

Water is used as a coolent in automobile radiators owing to its high specific heat capacity.

During conversion of water into steam, temperature remains constant
For phase conversion
or

where, is latent heat of steam.