ZEROTH LAW OF THERMODYNAMICS

 

Introduction:

Zeroth law of thermodynamics is one of the four laws of thermodynamics. The credit for formulating the law goes to Ralph H. Fowler. Interestingly, the zeroth law of thermodynamics was actually developed much later than the original three laws. However, there was some confusion regarding the nomenclature, whether it should be named the fourth law or some other name. The complication arose because the new law gave a much clearer definition of the temperature and basically replaced what the other three laws had to state. Fowler finally came up with the name to end this conflict. The zeroth law of thermodynamics frames an idea of temperature as an indicator of thermal equilibrium.

 

Statement of Zeroth Law of thermodynamics:

There are also various ways to state the zeroth law of thermodynamics. However, in simple terms, it can be said, “Systems that are in thermal equilibrium exist at the same temperature”.

What is the Zeroth Law of thermodynamics in simple way:

When a body ‘A’ is in thermal equilibrium with another body b’, and also separately in thermal equilibrium with a body ‘C’, then body ‘B’ and ‘C’ will also be in thermal equilibrium with each other. This statement defines the zeroth law of thermodynamics. The law is based on temperature measurement.


There are also various ways to state the zeroth law of thermodynamics. However, in simple terms, it can be said, “Systems that are in thermal equilibrium exist at the same temperature”. Zeroth law of thermodynamics takes into account that temperature is something worth measuring because it predicts whether the heat will transfer between objects or not. This is true regardless of how the objects interact. Even if two objects are not in physical contact, heat still can flow between them, by means of radiation mode of heat transfer. Whereas, zeroth law of thermodynamics states that, if the systems are in thermal equilibrium, no heat flow will take place.

 

 

Equation of zeroth law of thermodynamics:

             

      a = b and b = c, then a = c.

 

Relation between Temperature & zeroth Law Of thermodynamics:

 

Having understood the zeroth law of thermodynamics, it is essential to know how the zeroth law of thermodynamics leads to the concept of temperature.  A body’s temperature is a thermodynamic variable determining a surface’s degree of hotness or coldness. A hot object has a higher temperature than a cold object with a lower temperature. We know that thermal equilibrium is reached when two bodies in touch reach a constant temperature since the temperature is a relative variable. Heat is transferred from a hot thing to a colder item, or, to put it another way, hot objects lose heat energy while cold objects acquire it. When the exchange of heat energy between two bodies in thermal contact stops, the bodies reach a constant temperature and thus attain thermal equilibrium.

      Mathematical theories frequently require an equivalence relation, which is a technique for determining whether two entities are the same or not. Because it allows for the mathematical concept of temperature and the presence of physical thermometers, the zeroth law is known as the equivalence relation of thermodynamics. The distinction between energy and temperature is an important notion. Knowing how much energy two separate items possess is insufficient to predict which way heat will travel when they come into contact. The direction of heat flow is determined by the relative temperatures of the two systems.

     Thermal equilibrium occurs when two things are in close proximity to each other and allow one to obtain energy from the other without transferring net energy. If no net energy is transferred between them when they are placed in contact, they are in thermal equilibrium even when they are not in contact. When two objects remain in contact for a long time, they usually reach a point of equilibrium.

 


 

Demonstration of zeroth law using thermometer:

If two different thermometers using alcohol and mercury respectively, are calibrated at ice point and steam point and the distance between ice point and steam point is divided into 100 equal parts then they are not guaranteed to give the same reading anywhere between the calibration points, but they will always give the same readings at the calibration points itself.

 


 

 

 

Zeroth law of thermodynamics examples:

• When a heated and a cold body are brought close together, the hot body loses heat and the cold body starts to heat up. But the transfer of heat flows from hotter to the colder body. The flow of heat stops when both the systems attain thermal equilibrium.

• If the cup of tea is 80°C and the surrounding temperature is 30°C , the tea will lose its heat until its temperature reaches 30 degrees. Here a hot cup of tea acts like the zeroth law of thermodynamics.


Importance of zeroth law:

The zeroth law is important for the mathematical formulation of thermodynamics. Mathematically, it makes the relation of thermal equilibrium between systems an equivalence relation, which can represent equality of some quantity associated with each system

 

Limitations:

 • Limitations of Zeroth law is that it cannot be derived from other laws and cannot be applicable for other kinds of equilibrium.

 • Zeroth law of thermodynamics just tells us about equality of temperature.

• It does not give any clue how the heat is being transferred.

 

Advantages: -

• The zeroth law is important for the mathematical formulation of thermodynamics.

 • Mathematically, it makes the relation of thermal equilibrium between systems an equivalence relation, which can represent equality of some quantity associated with each system.

 

Conclusion:

Even if two objects are not in physical contact, heat still can flow between them, by means of radiation mode of heat transfer. Whereas, zeroth law of thermodynamics states that, if the systems are in thermal equilibrium, no heat flow will take place.

 

References:

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Contributors:

1. Karan rathod

2. Vivekanand rathod 

3. Rajan raut

4. Sahil kumar

5. Vishal payyawar

6. Rahul wagh  

 

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