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Question
Explain the thermodynamics of the isochoric process.
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Solution
- A thermodynamic process in which the volume of the system is kept constant is called the isochoric process.
- A system does no work in its environment during an isochoric process.
- For an isochoric process, ΔV = 0, and from the first law of thermodynamics, ΔU = Q.
- The temperature of the system changes, i.e., ΔT ≠ 0.
- This means that for an isochoric change, all the energy added in the form of heat remains in the system itself and causes an increase in its internal energy. Also, as volume is unchanged, no work is done.
- The first law of thermodynamics for the isochoric process is, Q = ΔU ….(1)
The change in internal energy is given by,
ΔU = nCVΔT ….(2)
The work done is given by,
W = pΔV = 0 ….(∵ ΔV = 0)
From equations (1) and (2),
The heat exchanged is given by,
Q = ΔU = nCVΔT - p-V diagram of isochoric process is as shown below:
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