Question

What are Kelvin Planck's and Clausius' statements of the second law of Thermodynamics?

Answer 1

KELVIN-PLANK
An engine operating in a cycle cannot transform heat into work without some other effect on its environment.

This tells us that it is impossible to have 100% efficiency...it is not possible to convert ALL the heat absorbed into work...some of it goes wasted.

CLAUSIUS
An engine operating in a cycle cannot transfer heat from a cold reservoir to a hot reservoir without some other effect on its environment.

This is the idea behind a fridge. Food in the fridge doesn't get cold alone you need a motor to do it! Also, as a consequence, heat cannot flow from a cold to a hot body spontaneously!!!!

{Definitions from: H. C. Ohanian, Phisics - 2nd ed., London WW Norton & Co., 1985]