Entropy

From Conservapedia

Entropy is a measure of disorder or information content in a system, first postulated by Lazare Carnot in 1803.

The second law of thermodynamics states that entropy will always increase over time within a closed system, defining a closed system as one in which neither matter nor energy may enter or leave.

Contents 1 Definitions 1.1 Thermodynamic definition 1.2 Statistical mechanics definition 1 1.3 Statistical mechanics definition 2 2 See also 3 References

Definitions

Thermodynamic definition

In classical thermodynamics, if a small amount of energy dQ is supplied to a system from a reservoir held at temperature T, the change in entropy is given by

Statistical mechanics definition 1

If a system can be arranged in W different ways, the entropy is

S = k_BlogW

where k_B is Boltzmann's constant.

Statistical mechanics definition 2

Label the different states a thermodynamic system can be in by . If the probability of finding the system in state i is p_i, the entropy is

This definition is closely related to ideas in information theory, where the definition of information content is very similar to the definition of entropy.

See also

• History of the development of entropy

References