Law of Conservation of Energy

Law Of Conservation Of Energy: An Overview

In the field of Chemistry and Physics, the energy that is held by a system that is isolated is always constant. This law is known as the law of conservation of energy. Over time, the energy is conserved and remains constant. Sometimes the law is referred as the physical law and the law states that energy is something, which cannot be created. In addition, the law states that the energy cannot be destroyed too. The law proposes that energy that is held by a system can only be changed or transferred from one state to another state. The above statement can be explained in detail with the help of an example. The example of such is – Industrial areas have the use of dynamites and when dynamite blows up, the chemical energy conserved within the dynamite is converted into the kinetic energy, which eventually makes the blast possible. If someone does the calculation, to sum up, all the energy that has been released by the explosion in various forms, then the total energy transfer can be understood. Example of such forms of energy are heat, sound, potential energy released from the dynamite pieces and the final is kinetic energy, the person can get the actual amount of the chemical energy that was decreased during the combustion process of the dynamite. Within a given reference frame, the isolated system’s energy is conserved or constant.

Special Relativity Theory

There are two laws, and they are conservation of energy and the conservation of mass. In classical mechanics, these two laws have separated use. However, it has been seen that the energy can be converted from matter and matter can also be converted from energy. This theory is known as special relativity. This theory follows the famous equation E = MC2 by the well-known scientist Albert Einstein. Thus, it can be concluded that the energy and the mass both are conserved. Noether’s theorem rigorously proved that the conservation of energy is a consequence of translation symmetry of continuous-time. In simple words, the meaning of the above line is, over time there is no chance that happens in the law of physics.

Consequence Of The Law Of Energy

There is a consequence of the law of energy conservation and that is there is no system or material holding some energy, which can be delivered or supplied to the surrounding environment or systems, without the presence, supply or help of some external energy to the system. There is one consequence of the law of conservation of energy, which is very interesting and that is the non-existence of the first kind perpetual motion machine. The law of conservation of energy cannot be defined for the systems that do not include the symmetry of the time translation as it is not possible. An example of such is in the domain of general relativity, the curved space-time or in the domain of condensed matter of physics, the time crystals.
The famous chemist, physicist and German physician Julius Robert Mayer did the first discovery of this law of conservation of the energy. Julius Robert Mayer is also renowned because he is one of the founders of the law of thermodynamics. He discovered the law of the conservation of energy back in the year 1841. His discovery of this law is currently known as the first law of thermodynamics. In the initial stage, the Mechanical equivalent of the heat helped to demonstrate the modern principle of the conservation. Heat can neither be created nor destroyed was maintained by the caloric theory. The interchangeability of the heat and the work was entailed as a contrary principle by the conservation of the energy. In the year 1850, Scottish mechanical engineer William John Macquorn Rankine used this phrase the law of conservation of the energy.


Law Of Conservation Of Mass-Energy

After the discovery of the famous equation E = MC2 by Albert Einstein, the law of conservation of mass and the energy were merged into one law which is the law of conservation of Mass-Energy. The law states the combined form of the above laws that is mass and energy be neither destroyed nor created. The thermodynamic system which is also closed, that law states that –
Q = dU + δW.
This can be stated as, dU = δQ - δW.
Here, in the above equation, δQ is the amount of the energy quantity that is added to the selected system with the help of certain heating process. The term δW represents the amount of the energy quantity that is lost by the selected system because of the total work that is done by the system alone on the surrounding environment. The term dU is representing the amount of energy that is being changed internally of the system. The use of the term? before the symbol of work and the heat is indicating that there is an energy increment that is interpreted differently from the energy increment of the internal energy which is denoted by the dU. The working procedure or process of the system is referred by the work and the heat which is in the form of energy that is being added or subtracted to the system. When the system is in a thermodynamic equilibrium, which is, in fact, unchanged, a particular property of the system state is the internal energy of the system U. Thus, the amount of the energy that is added to the system as the result of the heating is termed with the help of δQ or by the term “heat energy”. This does not get referred to as a particular energy form. In the same way, the amount of energy that is lost during the work by the system is referred as the “work energy” or δW. Hence, it can be concluded that the total amount of the internal energy held by the thermodynamic system in a particular or specific state can be determined. However, no person cannot tell the amount of the internal energy that came inside the system because of heating or cooling including the amount of energy that went outside the system because of heating or cooling the thermodynamic system is a given particular present state. This cannot be determined as a result of the total work that the system performs.

Entropy And Quasi-Static System

The system state has a function, which is known as the Entropy. The use of the function Entropy is to provide the limitations about the conversion possibility of the heat into the work. For a system, which is simple and compressible, performs the work and that can be written as-
δW = P dv.
Here in the above equation, the used term P means the pressure that has been used. The term dV denotes the small volume change of the system. These both are the variables of the system. The heat energy equation is written as the –
δQ = T dS.
This above heat energy equation is for the system where the speed of the process is infinitely slow and idealized. This is known as the quasi-static system. This type of system can be regarded as the reversible system. Here, the heat that is being transferred from the source along with the temperature is infinitesimally above the normal system temperature. From the equation, the term T denotes the temperature and the other term dS denotes the entropy change in the system, which takes place in a small amount. The state of any system has variables and entropy and temperature are one such example of variables. There are some open systems where the mass included in the system can easily be exchanged with the surrounding environment. These systems have the use of several walls, which help the system to transfer mass through the rigid walls and this is separated from the transfer of the work and heat. In this case, the first law of the thermodynamics can be written as –
dU = δQ - δW + u′ dM.
Most of the terms that have been used in the equation are already described before. The term u′ is used to denote the energy of the internal system with respect to the per unit mass that has been added to the system. The measurement is done with the help of the surrounding, which takes place before the process. The term dM has been used to refer to the mass that is added to the system.


Beta Decay Emission

In the year 1911, a major discovery happened and that is the emission of beta decay from the electrons. The discovery was the beta decay emission, which was happening in a continuous manner but not in a discrete spectrum. This situation was contradicted the law of conservation of energy. Back then, the assumption was that the beta decay is nothing but an emission that is happening simply from the nucleus. Enrico Fermi resolved this problem in the year 1933 by proposing an accurate description of the beta decay. He said that the emission is from the electron along with an antineutrino. The antineutrino has one purpose and that is to carry away the missing energy.

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