State the first law of thermodynamics how can it be expressed mathematically
Answers
The first law of thermodynamics states that the change in internal energy of a system ΔU equals the net heat transfer into the system Q, plus the net work done on the system W.
In equation form, the first law of thermodynamics is, ΔU=Q+W
Here ΔU is the change in internal energy U of the system. Q is the net heat transferred into the system—that is, Q is the sum of all heat transfer into and out of the system. W is the net work done on the system.
According to the first law of thermodynamics, during any transformation, there is conservation of energy.
In the case of closed thermodynamic systems, it is stated as follows:
"During any transformation of a closed system, the variation of its energy is equal to the quantity of energy exchanged with the external environment, by thermal transfer (heat) and mechanical transfer (labor). "
ΔQ = ΔU + W
where,
Q = Heat supplied to system
U = Increase in internal energy
W = Work done by system
The variation of the energy of a system which undergoes a transformation can be expressed according to the following relation:
ΔE = ΔU + ΔEc + ΔEp = W + Q
ΔE = the sum of the different energy variations of the system.
ΔU = increase in internal energy
ΔEc = the variation of the macroscopic kinetic energy of the system
ΔEp = the variation of the potential energy of the system
ΔW = Work done by system
ΔQ = Heat supplied to a system