1st law of thermodynamics
It states, energy can neither be created nor be destroyed. The total energy of universe remains constant.
E2 = E1 + q + w
E2 – E1 = q = w
∆E = q + w is mathematical statement of 1st law of thermodynamics
‘q’ is not a state function, w is not a state function but q + w = ∆E is a state function.
a). For isothermal process: ∆E = 0, q = – w, i.e., heat absorbed by system is equal to work by the system.
b). For isochoric process: ∆V = 0, w = p ∆V = 0, ∆E = q", i.e., change in internal energy is e to heat exchanged with the surroundings at constant volume.
c). For adiabatic process: q = 0, ∆E = w, i.e., internal energy change is equal to work done on the system.