Zero Law of Thermodynamics

A Zero Law of Thermodynamics is physical phenomena law which states two systems are each, at the same time, in thermal equilibrium with third system, they are as well in thermal equilibrium with each other.

AKA: Zeroth Law of Thermodynamics.
Example(s)
- Thermal equilibrium.
Counter-Example(s)
See: Carnot Efficiency, Laws Of Thermodynamics, Perpetual Motion Machines, Thermodynamics, Physical System, Maxwell's Demon Thought Experiment.

References

2016

(Wikipedia, 2016) ⇒ https://www.wikiwand.com/en/Zeroth_law_of_thermodynamics
- The zeroth law of thermodynamics states that if two thermodynamic systems are each in thermal equilibrium with a third, then they are in thermal equilibrium with each other.

Two systems are said to be in the relation of thermal equilibrium if they are linked by a wall permeable only to heat and they do not change over time. As a convenience of language, systems are sometimes also said to be in a relation of thermal equilibrium if they are not linked so as to be able to transfer heat to each other, but would not do so if they were connected by a wall permeable only to heat. Thermal equilibrium between two systems is a transitive relation.

The physical meaning of the law was expressed by Maxwell in the words: "All heat is of the same kind". For this reason, another statement of the law is "All diathermal walls are equivalent".

The law is important for the mathematical formulation of thermodynamics, which needs the assertion that the relation of thermal equilibrium is an equivalence relation. This information is needed for a mathematical definition of temperature that will agree with the physical existence of valid thermometers.

2015

(NASA Website, 2015) ⇒ https://www.grc.nasa.gov/www/k-12/airplane/thermo0.html
- The zeroth law of thermodynamics begins with a simple definition of thermodynamic equilibrium. It is observed that some property of an object, like the pressure in a volume of gas, the length of a metal rod, or the electrical conductivity of a wire, can change when the object is heated or cooled. If two of these objects are brought into physical contact there is initially a change in the property of both objects. But, eventually, the change in property stops and the objects are said to be in thermal, or thermodynamic, equilibrium. Thermodynamic equilibrium leads to the large scale definition of temperature. When two objects are in thermal equilibrium they are said to have the same temperature. During the process of reaching thermal equilibrium, heat, which is a form of energy, is transferred between the objects. The details of the process of reaching thermal equilibrium are described in the first and second laws of thermodynamics.

The zeroth law of thermodynamics is an observation. When two objects are separately in thermodynamic equilibrium with a third object, they are in equilibrium with each other. As an illustration, suppose we have three objects as shown on the slide. Object #1 and object #2 are in physical contact and in thermal equilibrium. Object #2 is also in thermal equilibrium with object #3. There is initially no physical contact between object #1 and object #3. But, if object #1 and object #3 are brought into contact, it is observed that they are in thermal equilibrium. This simple observation allows us to create a thermometer. We can calibrate the change in a thermal property, such as the length of a column of mercury, by putting the thermometer in thermal equilibrium with a known physical system at several reference points. Celsius thermometers have the reference points fixed at the freezing and boiling point of pure water. If we then bring the thermometer into thermal equilibrium with any other system, such as the bottom of your tongue, we can determine the temperature of the other system by noting the change in the thermal property. Objects in thermodynamic equilibrium have the same temperature.

2010

(Halliday et al., 2010) ⇒ David Halliday, Robert Resnick, and Jearl Walker. "Fundamentals of physics extended". John Wiley & Sons, 2010.

2005

(Hyperphysics Encyclopedia, 2005) ⇒ http://hyperphysics.phy-astr.gsu.edu/hbase/thermo/thereq.html#c2
- The "zeroth law" states that if two systems are at the same time in thermal equilibrium with a third system, they are in thermal equilibrium with each other.

If A and C are in thermal equilibrium with B, then A is in thermal equilibrium with C. Practically this means that all three are at the same temperature, and it forms the basis for comparison of temperatures. It is so named because it logically precedes the First and Second Laws of Thermodynamics.

There are underlying ideas about heat associated with the zeroth law of thermodynamics, and one of those ideas was expressed by Maxwell as "All heat is of the same kind". If A is in thermal equilibrium with B, then every unit of internal energy that passes from A to B is balanced by the same amount of energy passing from B to A. This is true even if the atomic masses in A are different from those in B, and even if the amount of energy per unit mass in A is different because the material has a different specific heat. This implies that there is a measurable property that can be considered to be the same for A and B, a property upon which heat transfer depends. That property is called temperature.

1963

(Feynman et al., 1963) ⇒ Richard P. Feynman, Robert B. Leighton and Matthew Sands (1963, 1977, 2006, 2010, 2013) "The Feynman Lectures on Physics": New Millennium Edition is now available online by the California Institute of Technology, Michael A. Gottlieb, and Rudolf Pfeiffer ⇒ http://www.feynmanlectures.caltech.edu/