# Second law of thermodynamics/Related Articles  Main Article Discussion Related Articles  [?] Bibliography  [?] External Links  [?] Citable Version  [?] A list of Citizendium articles, and planned articles, about Second law of thermodynamics.
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## Parent topics

• Physics [r]: The study of forces and energies in space and time. [e]
• Chemistry [r]: The science of matter, or of the electrical or electrostatical interactions of matter. [e]
• Engineering [r]: a branch of engineering that uses chemistry, biology, physics, and math to solve problems involving fuel, drugs, food, and many other products. [e]

## Other related topics

• Energy (science) [r]: A measurable physical quantity of a system which can be expressed in joules (the metric unit for a quantity of energy) or other measurement units such as ergs, calories, watt-hours or Btu. [e]
• Enthalpy [r]: Energy function of thermodynamic system equal to internal energy plus pV (pressure times volume). [e]
• Entropy (thermodynamics) [r]: Thermodynamic variable S appearing in the second law of thermodynamics. [e]
• Heat [r]: A form of energy that flows spontaneously from hotter to colder bodies that are in thermal contact. [e]
• Ideal gas law [r]: Relates pressure, volume and temperature for hypothetical gases of atoms or molecules with negligible intermolecular forces. [e]
• Internal energy [r]: Energy of a system in absence of interaction of the system with external fields [e]
• Joule-Thomson effect [r]: The increase or decrease in the temperature of a real gas (as differentiated from an ideal gas) when it is allowed to expand freely at constant enthalpy (meaning that no heat is transferred to or from the gas, and no external work is extracted from the gas). [e]
• Laws of thermodynamics [r]: Laws which describe the specifics for the transport of heat and work in thermodynamic processes. [e]
• Non-equilibrium thermodynamics [r]: Add brief definition or description
• Specific heat ratio [r]: The ratio of the specific heat of a gas at constant pressure, $C_{p}$ , to the specific heat at constant volume, $C_{v}$ , also sometimes called the adiabatic index or the heat capacity ratio or the isentropic expansion factor. [e]
• Vapor-compression refrigeration [r]: One of the many available refrigeration systems and very probably the most widely used system. [e]