The First Law of Thermodynamics - Energy is conserved.
The internal energy of a system is the sum of all the kinetic and potential energies of all its components.
ΔE = Efinal − Einitial
The equation above indicates the change in internal energy, ΔE, is the difference between the final energy, Efinal, and the initial energy, Einitial.
Thermodynamic quantities like ΔE have three parts: a number, a unit, and a sign.
- The number and unit give the magnitude of the charge.
- The sign gives the direction.
- A positive ΔE, when Efinal > Einitial, indicates the system gained energy from its surroundsings. (diagram B below)
- A negative ΔE, when Efinal < Einitial, indicates the system lost energy to its surroundsings. (diagram A below)