Second Law Of Thermodynamics - Practice Questions & MCQ

• Clausius's statement-It is impossible for a self-acting machine to transfer heat from a colder body to a hotter one

without the aid of an external agency.

• Kelvin’s statement-It is impossible for a body or system to perform continuous work by cooling it to a
  a temperature lower than the temperature of the coldest one of its surroundings.
• Kelvin-Planck’s statement-It is impossible to design an engine that extracts heat and fully utilizes it into work
  without producing any other effect.

These above statements are completely equivalent to the Second Law of Thermodynamics.

          This explains that the efficiency of an engine is always less than unity because heat cannot be fully converted into work.

It also explains that heat cannot flow from a body at a low temperature to one at higher temperatures unless work is done by an external agency.