Before considering the first and second law of thermodynamics, it is necessary to define what is meant by the term "thermodynamics."In this case, the word speaks for itself: it is easy to determine the other two - "thermal" and "dynamic".When Greek turns "heat, temperature" and "strength, movement, change."In other words, thermodynamics is a branch of physics that studies the features of conversion of heat into other forms of energy, and vice versa.At the same time the thermal motion of the objects of a microcosm (atoms, molecules, particles) is not included in the said section and studied in other areas of science.Thermodynamics also deals with the whole macro systems, which are characterized by volume, pressure and so forth.
This science is based on some basic features (zero, first, second law of thermodynamics), adopted in the postulates.They were determined experimentally and confirmed by theoretical calculations.The relationship between them only indirectly, since the beginning of the direct output of one from the other can not be performed.
There are four start - from zero to third.We point out the meaning of each.Zero law of thermodynamics states that any system tends to thermodynamic equilibrium, so the disappearance of external action in the end there is a balance.It may be an isolated system indefinitely.
One of the key - it is the first law of thermodynamics.It was first formulated in the 19th century.In fact, it is the law of conservation of energy in relation to what is happening in macrosystems thermodynamic processes.By the way, it is often with the help of this postulate is denied the possibility of existence of perpetual motion, since it is necessary to carry out work outside the reporting system, additional energy.According to him, in a closed isolated system value of energy always remains the same.
second law of thermodynamics is familiar to everyone from childhood.According to this, thermal energy can naturally be transmitted only in one direction - from a more heated to a less heated body.For example, it therefore seems winter outdoors cold as the ambient temperature is lower than that of the human body, which causes heat transfer.Second Law of Thermodynamics is one of the most famous.One of its consequences suggests that the entire internal energy of the system can not be fully converted into useful work.Interestingly, the second law of thermodynamics can not be proved mathematically.By setting the set of experiments was derived this law, later adopted as an axiom.
which is one of the aspects that characterize the second law of thermodynamics?Entropy!The term is translated from Greek means "transformation."Entropy is characteristic for any thermodynamic system and is a function of the state.In general it can be assumed that the entropy indicates a commitment to any system disorder.R. Clausius, who proposed the term for thermodynamic processes, as an explanation cited the example of the freezing water: the water present in the liquid state at the boundary of zero degrees Celsius.It is worth it to report a portion of the external energy, sufficient for imbalance, the liquid turns into a solid state (ice).At the same time due to internal changes in the structure of the energy is released.In this case it is a reversible process.Accordingly, the variation of entropy is the ratio of the total amount of thermal energy to the absolute temperature value.One of the consequences indicate that in closed systems without any external influence entropy increases.
