Question

Define first law of thermodynamics. Give its mathematical expression. 1

Answer 1

Hey There! The first law of thermodynamics is a version of the law of conservation of energy, adapted for thermodynamic systems. The law of conservation of energy states that the total energy of an isolated system is constant; energy can be transformed from one form to another, but can be neither created nor destroyed.


It' s mathematical expression is :- ΔU=Q+W

Answer 2

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