Write the first law of thermodynamics for an isothermal expansion process.

(N/A) The first law of thermodynamics is given by the equation: $\Delta Q = \Delta U + \Delta W$,where $\Delta Q$ is the heat supplied to the system,$\Delta U$ is the change in internal energy,and $\Delta W$ is the work done by the system.
In an isothermal process,the temperature of the system remains constant $(T = \text{constant})$.
Since the internal energy of an ideal gas depends only on its temperature,for an isothermal process,the change in internal energy is zero $(\Delta U = 0)$.
Substituting this into the first law of thermodynamics,we get: $\Delta Q = \Delta W$.
This means that in an isothermal expansion,the entire amount of heat supplied to the system is used to perform work by the system.