# 1 Law of Thermodynamics in Physics Class 11

Differential form of the first law of the thermodynamic equation – The first law of thermodynamics for a closed system was expressed by Clausius in two ways. One possibility concerned cyclical processes and system inputs and outputs, but did not refer to increments in the internal state of the system. The other way was a gradual change in the internal state of the system and did not expect the process to be cyclical. The first law of thermodynamics is usually represented by the equation: this important state variable was first recognized by Clausius in 1850 and called U {displaystyle U}, but he did not name it at the time and defined it not only in terms of work, but also in terms of heat transfer in the same process. It was also independently recognized in 1850 by Rankine, who also called it U {displaystyle U}; and in 1851 by Kelvin, who then called it „mechanical energy” and later „intrinsic energy”. In 1865, after some hesitation, Clausius began to call his state function U {displaystyle U} „energy”. In 1882, it was named by Helmholtz as internal energy. [39] If only adiabatic processes were of interest and heat could be ignored, the concept of internal energy would hardly appear or would be necessary. Relevant physics would be largely covered by the concept of potential energy, as foreseen in Helmholtz`s work on the principle of conservation of energy of 1847, although this does not deal with forces that cannot be described by a potential, and therefore does not fully justify the principle. In addition, this work criticized Joule`s early work, which had been carried out until then. [40] A great merit of the concept of internal energy is that it frees thermodynamics from a limitation to cyclic processes and allows treatment in relation to thermodynamic states. Thermodynamics is the branch of physics that deals with the relationships between heat and other forms of energy.

In particular, it describes how thermal energy is converted into and from other forms of energy and how it affects matter. The basic principles of thermodynamics are expressed in four laws. It is impossible to design a machine that can continuously provide mechanical work without consuming energy at the same time. Such a hypothetical machine is known as a perpetual motion machine of the first type. These types of machines violate the 1st law of thermodynamics and do not exist in reality. There are four laws of thermodynamics. They talk about temperature, heat, work and entropy. They are used in thermodynamics and other sciences, such as chemistry. The first law of thermodynamics states that the total energy of an isolated system is constant. Energy can be transformed from one form to another, but it cannot be generated or destroyed. The first law of closed-system thermodynamics was originally induced by empirically observed evidence, including calorimetric evidence. However, it is now understood to provide the definition of heat via the law of energy conservation and the definition of work in relation to changes in the external parameters of a system.

The original discovery of the law occurred gradually over a period of perhaps half a century or more, and some of the first studies related to cyclical processes. [5] For the thermodynamics of closed systems, the distinction between energy transfer as work and as heat is central and falls within the scope of this Article. For the thermodynamics of open systems, such a distinction would be beyond the scope of this article, but some limited comments on this subject are made in the next section entitled „First Law of Thermodynamics for Open Systems”. Energy can be divided into two parts, according to David McKee, a professor of physics at Missouri Southern State University. One is our macroscopic contribution to the human scale, like a piston moving and pressing on a gas system. Conversely, things happen on a very small scale where we can`t track individual messages. There is a sense in which this kind of additivity expresses a fundamental postulate that goes beyond the simplest ideas of classical thermodynamics of closed systems; the extensivity of some variables is not obvious and requires explicit expression; In fact, one author goes so far as to say that it could be recognized as a fourth law of thermodynamics, although this is not repeated by other authors. [79] [80] In an open system, particles and energy can be transferred to or from the system during a process. In this case, the first law of thermodynamics always applies in the form that internal energy is a function of the state and that the change of internal energy in a process is only a function of its initial and final state, as mentioned in the next section entitled First Law of Thermodynamics for Open Systems.

With such independence from the variables, the total increase in internal energy in the process is then determined as the sum of the internal energy transferred from the environment with the transfer of matter through the permeable walls to it, and the internal energy transmitted to the system as heat through the diathermic walls. and energy transferred to the system in the form of work through the adiabatic walls, including energy transferred to the system by long-range forces.

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