We know that thermodynamic processes (adiabatic, isothermal, isobaric or isovolumetric) produce variations in the characteristics of a system. We can use the First Law of Thermodynamics to verify energy conservation in thermodynamic processes.
Isothermal processes are those in which the system temperature is kept constant. in the diagram PV the curves that represent these processes are called isotherms. Two different isotherms do not intersect: if there was a common point, this point would correspond to two temperatures for the same value of P, V and no, What is impossible. See chart above.
For an ideal gas, energy only depends on temperature. When the temperature remains constant, the internal energy does not change.
If ∆T=0, then ∆U=0
By the first law of Thermodynamics, we have:
Q=τ+∆U
Q=τ
In an isothermal transformation, the gas can either yield or receive heat from the medium. When the gas receives heat, the work done is equivalent to the heat received. When the gas gives heat to the medium, the work done on the gas corresponds to the heat given up.
By Domitiano Marques
Graduated in Physics
Source: Brazil School - https://brasilescola.uol.com.br/fisica/primeira-lei-para-processos-isotermicos.htm