1st Law of thermodynamics
Haz clic aquí para modificar.
For thermodynamic calculations, we must first understand three principal concepts: Heat (Q), Work (W) and Internal energy (U), so heat is the transfer of thermal energy between two bodies at different at temperatures. Work is the force required to transfer energy between a system and its surroundings, it is also needed to create heat. Finally, Internal energy is the disordered motion of molecules (vibration, kinetic, rotational and potential energy) What is interesting about them is that together allow systems to exchange energy.
Theory
We can explain this relation of energies with the first law of Thermodynamics. It states that energy change from one form to another with the interaction of heat, work and internal energy. In other words: Energy can be neither created nor be destroyed, but it transforms from one form to another.
dU= dQ+ dW=0 or dU=dQ-PdV=0 The internal energy of a system decreases if the system gives off heat or does work. If the system gain energy (when the heat increases) then the internal energy increases as well. In other words, to know if the system gain or loses heat and work: -W-> comes in +W-> comes out +Q-> comes in -Q-> comes out It is also important to remember that the process could be at isochoric (dV=0), isobaric (dP=0), isothermal (dT=0) and adiabatic (insulation, Q=0) |