Second law of thermodynamics is about the extent and direction of energy transformation.
i) Kelvin’s statement
It is impossible to obtain a continuous supply of work from a body
by cooling it to a temperature below the coldest of its surroundings.
ii) Clausius statement
It is impossible for a self acting machine unaided by any external agency to transfer heat from a body at a lower temperature to another
body at a higher temperature.
(iii) Kelvin – Planck’s statement
It is impossible to construct a heat engine operating in a cycle, that
will extract heat from a reservoir and perform an equivalent amount of
work.