Q:

Sir,Is temperature a microscopic or macroscopic concept?

- Aqib (age 18)

Karachi,PAK

- Aqib (age 18)

Karachi,PAK

A:

The usual definition of temperature is T= dU/dS|_{V }where U is the internal energy of an object, S is its entropy, and "|V" means "at constant volume". This doesn't quite make sense for a microscopic object, for which specifying U may specify what state the object is in, and thus force S=0. So we usually think only of macroscopic objects as having a temperature.

There is a microscopic version of this meaning, however. Over time a microscopic system that can exchange energy with the outside will sample various different states with different energies. So you can define an average U and and S based on the*probabilities* of the different states. If these probabilities follow the right sort of pattern then you can talk about T of the time-averaged microscopic object.

Mike W.

There is a microscopic version of this meaning, however. Over time a microscopic system that can exchange energy with the outside will sample various different states with different energies. So you can define an average U and and S based on the

Mike W.

*(published on 02/16/2013)*