What are microstates and macrostates in statistical physics?

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SUMMARY

Microstates and macrostates are fundamental concepts in statistical physics, where microstates represent specific configurations of a system, such as the outcomes of coin tosses, while macrostates describe broader properties like the total number of heads. For instance, in five coin tosses, the macrostate defined by X (the total number of heads) can correspond to multiple microstates. Accessible states refer to microstates that a system can occupy without violating governing physical laws. Understanding these concepts is crucial for grasping the principles of entropy and statistical mechanics.

PREREQUISITES
  • Basic understanding of statistical mechanics
  • Familiarity with the concept of entropy in statistical thermodynamics
  • Knowledge of probability theory, particularly in relation to outcomes
  • Experience with combinatorial analysis, such as counting outcomes in experiments
NEXT STEPS
  • Study the concept of entropy in statistical thermodynamics
  • Explore the relationship between microstates and macrostates in various physical systems
  • Learn about combinatorial methods for calculating microstate configurations
  • Investigate applications of statistical mechanics in thermodynamic systems
USEFUL FOR

Students and professionals in physics, particularly those focusing on statistical mechanics, thermodynamics, and entropy analysis. This discussion is beneficial for anyone seeking to deepen their understanding of the foundational principles of statistical physics.

Lizwi
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Please help me, what are micro and macrostates, what are accessible states?
 
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Consider five coin tosses. I would call each of the possible outcomes a microstate (for example, HTTHT, THHHT, HHHTH, TTTTT and so on. H stands for heads and T for tails).

Now suppose I define a variable such as X=Total number of heads. For the microstates I have mentioned above, X will take values 2, 3, 4, 0 and so on. X is a macrostate. It tells you nothing about the specific configuration of the system. For example, X=4 will correspond to five microstates (HHHHT, HHHTH, HHTHH, HTHHH, THHHH), but you have no way of knowing which one.

An accessible state is a microstate the system can take without violating any laws governing the system.

I hope it is clear now.
 

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