Great question! Here’s how thermodynamic processes relate to the first law of thermodynamics:
The first law of thermodynamics is essentially the law of energy conservation applied to thermodynamic systems. It states that the change in the internal energy of a system (ΔU) is equal to the heat (Q) added to the system minus the work (W) done by the system on its surroundings: ΔU=Q−W\Delta U = Q – W
How Thermodynamic Processes Fit In:
A thermodynamic process describes how a system changes from one state to another — such as changes in pressure, volume, temperature, or internal energy. Different processes affect the amounts of heat transferred and work done differently, but they all must obey the first law.
- Isothermal process (constant temperature): Since temperature stays constant, the internal energy ΔU = 0 (for ideal gases). So, Q=WQ = W — the heat added to the system is fully converted into work done by the system.
- Adiabatic process (no heat exchange, Q=0Q=0): The system is thermally isolated, so the internal energy change is due solely to work done on or by the system: ΔU=−W\Delta U = -W.
- Isobaric process (constant pressure): Heat added changes both internal energy and does work by changing the volume.
- Isochoric process (constant volume): No work is done (W=0W=0), so the heat added changes internal energy directly: ΔU=Q\Delta U = Q.