Which of the following statements is incorrect about irreversible processes?
**Cyclic process** system returns to initial state, ΔU=0 over cycle, net work W_net = area enclosed in P-V diagram, Q_net = W_net from first law ΔU= Q - W =0 => Q_net = W_net, clockwise cycle work done by system positive, counterclockwise work done on system negative, efficiency η = W_net/Q_in. Irreversible processes (e.g., free expansion) involve non-equilibrium states or dissipation, preventing restoration without external effects. Option C is incorrect; they do not occur in equilibrium. Using first law ΔU = Q - W, W = ∫ P dV, isobaric W = P ΔV, isothermal W = n R T ln(V₂/V₁), adiabatic P V^γ =
Ref: NCERT > Physics Book > Thermodynamics > Cyclic Processes and Reversibility Concepts