Isochoric Process
V = const, W = 0, Q = ΔU.
Key Notes
Isochoric (or isovolumetric) process: volume stays CONSTANT (ΔV = 0).
No work done: W = P·ΔV = 0.
First law: Q = ΔU. All heat goes into internal energy.
Heat absorbed: Q = nC_v·ΔT.
On PV diagram: VERTICAL line.
Pressure-temperature link: P/T = constant (Gay-Lussac's law).
Examples: heating gas in a sealed rigid container, pressure cooker partially.
Used in Otto cycle (gasoline engine) — constant-volume heat addition (idealized).
Formulas
Equation
Gay-Lussac's law.
Work done
ΔV = 0 ⇒ no work.
Heat absorbed
Equal to ΔU.
First law (isochoric)
All heat goes to internal energy.
Important Points
Isochoric ⇒ ΔV = 0 ⇒ W = 0 ⇒ Q = ΔU.
Most direct conversion of heat to internal energy.
On PV diagram: VERTICAL line. No area swept ⇒ no work.
Doubling absolute T at constant V doubles pressure (Gay-Lussac).
Sealed rigid containers: heating them is purely isochoric.
Heat exchange ↔ internal energy directly — no work distraction.
Isochoric Process notes from sciphylab (also known as SciPhy, SciPhy Lab, SciPhy Labs, Physics Lab). Class 11 physics revision for JEE Mains, JEE Advanced, NEET UG, AP Physics 1/2/C, SAT, and CUET-UG.