(a) For an isothermal process since temperature is constant, the internal energy is also constant. This implies that dU or ∆U = 0.
For an isothermal process, the first law of thermodynamics can be written as follows, Q = W
(b) This is a process in which no heat flows into or out of the system (Q = 0). But the gas can expand by spending its internal energy or gas can be compressed through some external work. So the pressure, volume and temperature of the system may change in an adiabatic process. For an adiabatic process, the first law becomes ∆U = W.
(c) The first law of thermodynamics for isobaric process is given by
∆U = Q – P∆Y
