Entropy change in reversible process

The second law of thermodynamics applied to a closed system and an idealized, reversible or quasistatic process, states that in such a process of transfer of energy as heat to closed thermodynamic system \(B\), which allows energy but not matter exchanges, from an auxiliary thermodynamic system \(A\), an infinitesimal increment in the entropy of system \(B\) is defined to result from an infinitesimal transfer of heat to system \(B\) divided by the common thermodynamic temperature of systems \(A\) and \(B\).

Notation:

1. \(\delta\) (delta) denotes an inexact, path-dependent differential.

2. \(d\) denotes an exact, path-independent differential.

Notes:

1. Also applicable to actually possible quasi-static irreversible processes without composition change

Links:

1. Wikipedia.

entropy_change

Infinitesimal change in entropy of system \(B\).

Symbol:

dS

heat

Infinitesimal amount of heat transferred to system \(B\).

Symbol:

delta(Q)

Latex:

\(\delta Q\)

common_temperature

Common temperature of systems \(A\) and \(B\).

Symbol:

T

Latex:

\(T\)

Dimension:

temperature

law

dS = delta(Q) / T

Latex:

\[dS = \frac{\delta Q}{T}\]