Isochoric process

Isochoric Process Experiment for Schools, Teachers, and Students

An isochoric process is a thermodynamic process in which the volume of the system remains constant. Since the volume does not change, no work is done during the process. Mathematically:
ΔV = 0 and W = P ΔV = 0

Key Features of an Isochoric Process:

• The system’s volume remains constant throughout the process.
• No work is done by or on the system since there is no change in volume.
• Any heat energy (Q) supplied or removed changes only the internal energy (ΔU) of the system.
• The pressure and temperature of the system may change.

First Law of Thermodynamics for an Isochoric Process:

ΔQ = ΔU
Where:

• ΔQ: Heat added or removed from the system,
• ΔU: Change in the internal energy of the system.

Relation Between Pressure and Temperature:

For an ideal gas undergoing an isochoric process:
(P1 / T1) = (P2 / T2)
Where:

• P1, T1: Initial pressure and temperature,
• P2, T2: Final pressure and temperature.

Heat Supplied in an Isochoric Process:

ΔQ = n C_v ΔT
Where:

• n: Number of moles of the gas,
• C_v: Molar specific heat at constant volume (J/mol·K),
• ΔT = T2 – T1: Change in temperature.

Examples of Isochoric Processes:

• Heating or Cooling in a Sealed Container: When a gas in a rigid container is heated or cooled, its pressure changes without any change in volume.
• Automotive Engines: The fuel-air mixture in an engine’s cylinder undergoes an isochoric process during the ignition phase, where the volume is fixed.
• Pressure Cooker: In a pressure cooker, the volume of the steam and water remains constant, while the temperature and pressure increase.

Applications of Isochoric Processes:

• Design of Rigid Containers: Used in the analysis of systems where volume is constant, such as pressure vessels.
• Thermodynamic Cycles: Isochoric processes are part of thermodynamic cycles, like the Otto and Diesel cycles, in automotive engines.
• Heat Measurement: Specific heat at constant volume (C_v) is determined using isochoric processes.

Graphical Representation:

1. Pressure-Volume (P-V) Graph: An isochoric process appears as a vertical line since the volume remains constant.
2. Temperature-Pressure (T-P) Graph: Pressure is directly proportional to temperature for an ideal gas, resulting in a straight line.

Observations:

• No work is done in an isochoric process as the volume is constant (W = 0).
• Any heat energy (ΔQ) changes only the internal energy of the system.
• Pressure and temperature are directly proportional in an ideal gas during an isochoric process.

Isochoric processes are fundamental in thermodynamics, describing systems with constant volume. They are widely used in engineering and scientific applications where heat transfer impacts only internal energy without performing work.