First Law of Thermodynamics

The First Law of Thermodynamics states that energy cannot be created or destroyed, only converted from one form to another. It is a statement of conservation of energy.

Mathematical Expression

The First Law can be expressed as:

ΔU=QW\Delta U = Q - W

Where:

  • ΔU = change in internal energy
  • Q = heat added to the system
  • W = work done by the system

Key Concepts

  • Internal Energy (U) is a state function
  • Heat (Q) is positive when added to system
  • Work (W) is positive when done by system
  • Path independence of ΔU

Applications

  • Heat engines and power plants
  • Refrigeration systems
  • Industrial processes
  • Natural phenomena