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First Law

First Law of Thermodynamics Equation


$$ \Delta U = Q - W $$ where:

Δ U   =   Change in internal energy   (J)

Q   =   Heat added to the system   (J)

W   =   Work done by the system   (J)


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Equation Assumptions


  • Energy is conserved.
  • System boundaries are well defiend.
  • There are no chemical reactions or phase changes.