Which process is described as having constant entropy in the material?

Which process is described as having constant entropy in the material?

• A. Isotropic Process
• B. Isentropic Process
• C. Isobaric Process
• D. Isothermal Process

Answer: (A)

Constant entropy means the system’s entropy does not change as the process proceeds. This happens in an isentropic path, the idealized reversible adiabatic process where no heat enters or leaves the system and no irreversibilities generate entropy. Since entropy change for a reversible process equals the heat transfer divided by temperature, dS = δQ_rev / T, having zero heat transfer (δQ_rev = 0) leads to dS = 0, so S remains constant. For an ideal gas, an isentropic process follows specific relations such as pV^γ = constant and T V^(γ−1) = constant, where γ is the heat capacity ratio. This shows how pressure and temperature evolve with volume while entropy stays fixed. In contrast, keeping temperature constant (isothermal) or pressure constant (isobaric) does not guarantee constant entropy, and isotropic describes a material having identical properties in all directions, which is not a thermodynamic path related to entropy change.

Constant entropy means the system’s entropy does not change as the process proceeds. This happens in an isentropic path, the idealized reversible adiabatic process where no heat enters or leaves the system and no irreversibilities generate entropy. Since entropy change for a reversible process equals the heat transfer divided by temperature, dS = δQ_rev / T, having zero heat transfer (δQ_rev = 0) leads to dS = 0, so S remains constant.

For an ideal gas, an isentropic process follows specific relations such as pV^γ = constant and T V^(γ−1) = constant, where γ is the heat capacity ratio. This shows how pressure and temperature evolve with volume while entropy stays fixed.

In contrast, keeping temperature constant (isothermal) or pressure constant (isobaric) does not guarantee constant entropy, and isotropic describes a material having identical properties in all directions, which is not a thermodynamic path related to entropy change.