Which of the following quantities is not part of Bridgman's thermodynamic equations?

Bridgman's thermodynamic equations, developed by physicist Percy Bridgman, are foundational in the field of thermodynamics. They focus on the relationship between various thermodynamic quantities, typically including internal energy, temperature, pressure, and volume.

The correct choice indicates that entropy, while a crucial thermodynamic property, is not explicitly part of Bridgman's set of equations. Bridgman emphasized quantities that can be directly measured and manipulated in experiments, such as internal energy, temperature, and pressure. Entropy, representing the degree of disorder in a system and often considered in the context of the second law of thermodynamics, is more abstract and is not a primary focus of Bridgman’s equations.

Internal energy indicates the total energy contained within a system, temperature signifies the thermal state of the system, and Gibbs free energy relates to the amount of reversible work obtainable from a thermodynamic system at constant temperature and pressure. While these are critical aspects of thermodynamics, they don’t include entropy within the framework he established, which is why the choice referring to entropy is the correct one.