Corollaries of first law of thermodynamics:

First law of thermodynamics has significant corollaries.

Corollary 1: (First Law for process).

There exists property of closed system; the change in value of this property during the process is given by the difference between heat supplied and work done.

    dE = dQ - dW

Here E is property of system and is called as total energy that includes internal energy, kinetic energy, potential energy, electrical energy, magnetic energy, chemical energy, etc.

Corollary 2: (Isolated System).

For the isolated system, heat and work both interactions are absent (d Q = 0, d W = 0) and E = constant. Energy can neither be created nor be destroyed; but, it can be converted from one form to other. 

Corollary 3: (PMM - 1).

A perpetual motion machine of first kind is almost impossible.