Imagine a process that has resulted in the production of some work, but does not alter in any way the other bodies.The mechanism of implementing such a process is called a perpetual motion machine of the first kind.The inability to create a "perpetual motion" in this case stems from the first law of thermodynamics.
first law of thermodynamics is mathematically formulated as follows: Q = U (2) - U (1) + A (1-2), where Q - the quantity of heat received by the system, U (2) - Internalenergy of the system at the end of the process, U (1) - the internal energy of the system at the beginning of the process, A (1-2) - the external work done by the system.
So, the heat received by the system, it is spent on th
e commission of external work and the increment of its internal energy ΔU = U (2) - U (1).
Perpetuum mobile requires the following conditions: U (1) = U (2) - the internal energy of the system does not change throughout the process; Q = 0 - the system does not receive any amount of heat from the outside.
Substituting these conditions in the first law of thermodynamics, it turns out that A (1-2) = 0;system does not produce external work.Thus, the impossibility of constructing a perpetual motion machine of the first kind is proved.
Eternal engine second kind - a hypothetical heat engine with an efficiency of 100%.It is assumed that such a machine can be converted into work all the heat resulting from the thermal reservoir.
Experimental data indicate that build perpetual motion machine of the second kind is impossible.The generalization of experimental facts became postulate second law of thermodynamics, which says it is the impossibility of creating a perpetual motion machine of the second kind.So far, the consequences of this thermodynamic postulate did not find any experimental refutation.