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#conceptual

3 public questions tagged with this topic.

Cyclic Processes and Reversibility Concepts

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

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Cyclic Processes and Reversibility Concepts

Which of the following statements is correct about extensive variables?

**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. Extensive variables (e.g., volume, internal energy) scale with the system’s size, halving when the system is halved, unlike intensive variables (e.g., pressure). Option C is correct. 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

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Specific Heat Capacity and Latent Heat

Which of the following statements is incorrect about work in thermodynamics?

**Latent heat** energy needed for phase change without temperature change, overcomes intermolecular forces, e.g., heating ice at 0°C to water at 0°C requires 334 kJ/kg, then heating water to 100°C requires c ΔT, then vaporization 2260 kJ/kg, illustrating two types of heat. Work ( W = P Δ V ) is path-dependent, not a state variable, and involves mechanical energy transfer, not temperature differences (unlike heat). Option C is incorrect. 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 = const and η = 1 -

Ref: NCERT > Physics Book > Thermodynamics > Specific Heat Capacity and Latent Heat

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