Comparatively Explanation on the first and the second law of thermodynamics
It is essential to know the difference between the two laws of thermodynamics. The first law is actually the special form of the conservation principle of energy. The first law proposes that both heat and mechanical energy are different forms of energy and it is possible to transform one form to another form. Besides this, during transformation one is equivalent to the other, this is also known from the first law of thermodynamics. In reality although we can transform a fixed amount of work into heat, but the planning of transformation of a fixed amount of heat into work is not possible. Or, where is the origin of heat— a hot body or a cold body? We do not get answers of these questions from the first law of thermodynamics. Answers of all these questions are the matter of discussion of the second law of thermodynamics.
According to the second law of thermodynamics, when heat is transformed into work then a portion of that is transformed into work, but all amount of heat is not transformed into work. In addition to it, simultaneous presence of a hot and a cold body is always needed for the transformation. While flowing heat from a hot body to a cold body some work is done.