What cycle process has constant pressure?

What cycle process has constant pressure?

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

Answer: (A)

Constant pressure means the external pressure acting on the system stays fixed while other state variables can change. In a cycle, an isobaric step keeps pressure the same while volume (and often temperature) changes. On a PV diagram this is a horizontal line, since P is constant as V varies. The gas does work during this leg equal to W = P ΔV, because the boundary moves at the constant pressure. For an ideal gas, keeping P fixed also ties volume and temperature together via PV = nRT, so heating at constant pressure increases both V and T. This differs from other processes: an isothermal step keeps temperature constant, so PV = nRT with T fixed and V changing; an isentropic step involves no heat transfer and constant entropy; an isochoric step keeps volume fixed, so no boundary work occurs and pressure changes with temperature.

Constant pressure means the external pressure acting on the system stays fixed while other state variables can change. In a cycle, an isobaric step keeps pressure the same while volume (and often temperature) changes. On a PV diagram this is a horizontal line, since P is constant as V varies. The gas does work during this leg equal to W = P ΔV, because the boundary moves at the constant pressure. For an ideal gas, keeping P fixed also ties volume and temperature together via PV = nRT, so heating at constant pressure increases both V and T.

This differs from other processes: an isothermal step keeps temperature constant, so PV = nRT with T fixed and V changing; an isentropic step involves no heat transfer and constant entropy; an isochoric step keeps volume fixed, so no boundary work occurs and pressure changes with temperature.