Clausius Statement

Dhristi JEE 2022-24

What is Clausius Statement?

It is nearly impossible for heat to move by itself from a temperature that is lower in temperature to a reservoir that is at a higher temperature. That is we can say that the transfer of heat can only occur spontaneously from high temperature to temperature. For example, we cannot construct a refrigerator that can operate without any input work.

That is, the transfer of heat can only occur spontaneously in the temperature direction which decreases. 

Clausius Theorem

The theorem of Clausius in 1855 states that for a thermodynamic system, that is the heat engine or even heat pump exchanging heat with external reservoirs and thermodynamics undergoing of a cycle follows the inequality given by


\[\frac {∮δQ}{T}<0\]


Statement Which is of Celcius 

This is the amount of infinitesimal heat which is absorbed by the system from the reservoir and is the external temperature of a reservoir that is surrounded at a particular instant in time. The integral which is closed is carried out along a process of thermodynamic process path from the initial/final state to the same initial/final state. In principle, the closed integral can start and end at a point that is arbitrary along the path.


If there are multiple reservoirs with different temperatures then the inequality of Clausius reads the following:


\[∮ (\frac {δQ_1}{T_1} + \frac {δQ_2}{T_2} +.... \frac {δQ_n} {T_n}) < 0 \]


In the case of a process that is reversible, then it holds equality. The case which is reversible is used to introduce the function of the state which is known as entropy. This is because in a process that is cyclic the variation of a state function is zero. In other words, we can say that the Clausius statement says that it is impossible to construct a device whose only effect is the transfer of heat from a reservoir that is cool to a hot reservoir. Equivalently the spontaneously flows of heat from a hot body to a cooler one.

The generalization is Clausius inequality.


History of Clausius theorem 

The theorem of Clausius is an explanation of mathematics of the thermodynamics second law. It was developed by Rudolf Clausius who explained the relationship between the flow of heat flow in a system and the entropy of the system and its surroundings. The development of Clausius in his efforts to explain entropy is quantitatively defined. In items that are direct terms, the theorem gives us a way to determine if a process of cyclical is irreversible or reversible. The theorem of Clausius provides a formula that is quantitative for understanding the second law.


Clausius was one of the first to work on the idea of entropy and he is even responsible for giving that name to the theorem. What is now known as the theorem of Clausius was first published in 1862 in Clausius' ``On the Application of the Theorem of the transformation Equivalence to Interior Work". Sought Clausius to show a proportional relationship which is between entropy and the energy flow by heating defined by the symbol δQ into a system. 


In a system, the energy of heat can be transformed into work, and the work can be transformed into heat through a process that is cyclical. Clausius writes that The algebraic sum of all the transformations which are occurring in a process that is cyclical can only be less than zero, or, as a case of extreme equal to nothing. In other words, we can say that the equation is given below:


\[\frac {∮δQ} {T} = 0\]


Clause Statement of Second Law of Thermodynamics

In 1850 Here we can see that one of the earliest statements of the thermodynamics Second Law was made by R. Clausius. He stated the following in the next line.


“It is very impossible to construct a device that operates on a cycle and whose effect is the heat transfer from a body which was cooler to a hotter one. 


Heat spontaneously cannot flow from the system of cold to the hot system without external work being performed on the system. This is exactly what heat pumps and refrigerators accomplish. In a heat flow or the refrigerator from the body which is cold to hot, but only when forced by an external work, the refrigerators are driven by motors which are electric and require work from their surroundings to operate.


The Clausius statement of law states the following:

It is nearly impossible for any system to operate in a way such that the sole result would be a transfer of energy by heat from a cooler to a hotter body.

Heat can be transferred from a body that is cooler to a body that is hotter if other effects accomplishing the heat transfer occur within the surrounding system or both. Air conditioners or AC and refrigerators are devices that are supposed to transfer heat from a cool space to its hot surroundings. But in both cases, they need power input. The statement which is of Clausius says that an air conditioner won't cool a room without power input.

Kelvin-Planck Statement of the Second Law

An engine or a heat engine must reject some energy to sink the heat to run a cycle. That is no engine of heat that can convert all the heat it received from a temperature of the high source to work. It is the basis for the Plancks of Kelvin statement of the thermodynamics second law which is given as:


It is impossible for any of the systems to operate in such a cycle of thermodynamics and deliver an equivalent amount of work which is to its surroundings while receiving energy by transfer of heat from a single thermal reservoir.

The Planck Kelvin statement puts forward the idea that no engine of heat can have 100 percent efficiency.


This is all about the Clausius Statement explaining thermodynamics and its related terms. Focus on the history of this statement and how it defines the laws of thermodynamics to grab hold of the concept.

FAQs on Clausius Statement

1. What is the Statement of Clausius?

Clausius has given the is that It is impossible to make a device that operates on a product and cycles. There is no other effect than the transfer of heat from a cooler to a body that is hotter.

2. What is a Clausius Example Statement of the Second Law of Thermodynamics?

It is impossible to design a device that works on a product and cycles with no other effect other than a transfer of heat from a cold body to a hot body. That is, the heat transfer can only occur spontaneously in the direction of decreased temperature.

3. What is the Statement Planck Kelvin of the Second Law of Thermodynamics?

The plank Kelvin statement or we can say that the Heat Engine Statement which is of the second law which is of thermodynamics states that it is impossible to devise a cyclically operating engine of heat. The effect of which is to absorb the energy in the form of heat from a thermal single which is a reservoir and to deliver an equivalent amount of work.

4. What is the Statement of the Thermodynamics Second Law?

In terms of the engine of heat and the thermodynamics second law states that it is impossible to convert the heat from a source that is of single-source into work without any other effect. This is called the statement of Kelvin of the thermodynamics second law.