Laws of Thermodynamics

Thermodynamics is the study of systems which involves energy transfer in the form of heat and work. The first law of thermodynamics states that energy cannot be created nor destroyed but can be converted from one form to the other. This energy is always conserved. It can also be said to refer to the thermodynamic processes in which heat and work can be distinguished and measured . In the form of an equation, the conversation of energy equation can be represented as:

First law of thermodynamics:        U= Uf +U0 = Q – W


Where U represents the internal energy, Q represents heat and W represents the work done. Therefore, the change in internal energy of a system is equal to the difference between heat produced and the work done on the system. Q (heat) is negative if heat is removed and positive if heat is added to the system; W (work done) is negative if work is done on the system and positive if work is done by the system.

The second law of thermodynamics (also called the Law of increased Entropy) states that, in all energy changes, if no energy leaves or enters the system, the energy of the system will always be less than the energy of its initial state. This is also referred to as entropy. Entropy is a measure of unusable energy within an isolated system. For example, in a heat engine it is not possible to extract any amount of heat from a reservoir which is hot and use it all to do work, some amount of heatmust be exhausted to a cold reservoir.

The second law, therefore, distinguishes between irreversible and reversible physical processes.  It expresses the irreversibility of actual physical processes by stating that the entropy of an isolated macroscopic system never decreases.

High quality energy has a low-entropy value and cannot be recycled after use. From the entropy law, changing energy from a state of high-quality to a state of low-quality state can only be done once. There is no way that you can recycle the low-quality energy from the low quality energy state to high-quality energy. This is because; during the process of energy transformation, there is always an intrinsic production of entropy that can never be reversed.

From the second law of thermodynamics, energy cannot be recycled. This is because as the energy is transformed from one form of energy to another form of energy which leads to a loss of quality and becomes less useful. The energy available after the occurrence of a chemical reaction is always less than that at the beginning of the reaction. For example, in a car, not all of gasoline is used to run it. The majority of the oil gets dispersed into the atmosphere in the form of emissions.

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