Important Thermodynamic Processes to Know for AP Physics 2 (2025)

What is the First Law of Thermodynamics?

ΔU = Q - W, which states that the change in internal energy is equal to heat added to the system minus work done by the system.

What occurs during an Isothermal Process?

The system's temperature remains constant and the internal energy does not change (ΔU = 0).

In an Adiabatic Process, what is the heat exchange with surroundings?

No heat exchange occurs (Q = 0).

How is work done during an Isobaric Process calculated?

W = PΔV, where P is the constant pressure and ΔV is the change in volume.

During an Isochoric Process, what happens to the volume?

The volume remains constant (W = 0), and any heat added changes the internal energy (ΔU = Q).

What defines a Cyclic Process?

The system undergoes a series of processes and returns to its initial state, resulting in a net change in internal energy of zero (ΔU = 0).

What is an Isentropic Process?

A reversible adiabatic process where entropy remains constant (ΔS = 0).

What happens in a Throttling Process?

Pressure drops as a fluid passes through a restriction or valve without heat exchange (W = 0, Q = 0).

What does the Carnot cycle represent?

An idealized model of a heat engine that operates between a hot and cold reservoir with maximum efficiency.

How is the efficiency (η) of a heat engine calculated?

η = 1 - Tc/Th, where Tc is the temperature of the cold reservoir and Th is the temperature of the hot reservoir.

What characterizes a Polytropic Process?

It follows the relationship PV^n = constant, where n is the polytropic index.

What is the Coefficient of Performance (COP) in refrigeration cycles?

COP = Qc/W, where Qc is the heat removed from the cold reservoir and W is the work input.

What happens in a refrigeration cycle?

Heat is transferred from a low-temperature reservoir to a high-temperature reservoir.

In an Isothermal Process for an ideal gas, what is the work calculation?

W = nRT ln(Vf/Vi), where Vf and Vi are the final and initial volumes.

What is the relationship of heat capacities in an Adiabatic Process?

γ = Cp/Cv, where γ is the heat capacity ratio.

What is the concept of Entropy in thermodynamics?

Entropy is a measure of the disorder or randomness in a system, often associated with the amount of energy unavailable to do work.

What is a Heat Engine?

A heat engine is a device that converts thermal energy into mechanical work by taking in heat from a high-temperature source and expelling some heat to a low-temperature sink.

What is the significance of the Refrigeration Cycle?

The refrigeration cycle is significant because it allows for the transfer of heat from a cooler space to a warmer space, effectively cooling the lower temperature area, such as in refrigerators or air conditioners.

Define Internal Energy (U).

Internal energy is the total energy contained within a system, due to both the kinetic and potential energies of its microscopic components.

How do you define Enthalpy (H)?

Enthalpy is defined as H = U + PV, where U is the internal energy, P is the pressure, and V is the volume of the system, representing the total heat content.