Question

Expression of first law of thermodynamics in physics

Answer 1

The first law makes use of the key concepts of internal energy, heat, and system work. It is used extensively in the discussion of heat engines. ... It is typical for chemistry texts to write the first law as ΔU=Q+W. It is the samelaw, of course - the thermodynamic expression of the conservation of energy principle.

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