Which thermodynamic process is defined as constant volume?

Which thermodynamic process is defined as constant volume?

• A. Isothermal - no temperature change
• B. Isometric - constant volume
• C. Adiabatic - no heat exchange
• D. Isobaric - constant pressure

Answer: (B)

Constant volume means the system’s volume doesn’t change, so no boundary work is done (W = ∫ P dV = 0). In the first law, ΔU = Q − W, this gives ΔU = Q. For many substances, especially ideal gases, internal energy depends on temperature, so heating or cooling at fixed volume changes the temperature. The term used for this process is isometric (also called iso­choric), which directly describes the fixed-volume constraint. The other descriptions refer to different constraints: isothermal means temperature stays constant, adiabatic means no heat is exchanged with the surroundings, and isobaric means pressure stays constant.

Constant volume means the system’s volume doesn’t change, so no boundary work is done (W = ∫ P dV = 0). In the first law, ΔU = Q − W, this gives ΔU = Q. For many substances, especially ideal gases, internal energy depends on temperature, so heating or cooling at fixed volume changes the temperature. The term used for this process is isometric (also called iso­choric), which directly describes the fixed-volume constraint.

The other descriptions refer to different constraints: isothermal means temperature stays constant, adiabatic means no heat is exchanged with the surroundings, and isobaric means pressure stays constant.