Which process is characterized by no heat exchange between the system and its surroundings?
**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. An adiabatic process is defined by no heat transfer ( Δ Q = 0 ) between the system and surroundings. This occurs when the system is insulated or the process is too rapid for heat exchange. Using first law ΔU = Q - W, W = ∫ P dV, isobaric W = P ΔV,
Ref: NCERT > Physics Book > Thermodynamics > Cyclic Processes and Reversibility Concepts
