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#concept check

3 public questions tagged with this topic.

Heat Transfer Work Distinction and Internal Energy Change

Which of the following statements is incorrect about isothermal processes?

**Heat and work distinction** heat is energy transfer due to temperature difference, random molecular motion, work is organized energy transfer due to macroscopic force, e.g., piston movement, both path functions depend on process, not state, internal energy U state function depends only on state (T for ideal gas), ΔU path independent, Q and W path dependent but Q-W = ΔU path independent. For an ideal gas in an isothermal process ( T = constant ), Δ U = 0 , and heat balances work. Option B is incorrect; internal energy does not increase. Using first law ΔU = Q - W, W = ∫ P

Ref: NCERT > Physics Book > Thermodynamics > Heat Transfer Work Distinction and Internal Energy Change

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Specific Heat Capacity and Latent Heat

Which of the following statements is incorrect about a cyclic process?

**Heat capacity** at constant pressure C_p and volume C_v, C_p = C_v + R per mole, for solids Dulong-Petit C_v≈3R≈25 J/mol·K. Specific heat and latent heat govern temperature changes and phase transitions, Q = m c ΔT for heating, Q = m L for melting/boiling at constant T. In a cyclic process, Δ U = 0 since U is a state function, and net heat equals net work. Option A is incorrect; internal energy does not change over a complete cycle. Using first law ΔU = Q - W, W = ∫ P dV, isobaric W = P ΔV, isothermal W = n R T

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

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First Law of Thermodynamics Applications

Which of the following statements is incorrect about the Zeroth Law of Thermodynamics?

**First law applications** for isobaric W = P ΔV, Q = n C_p ΔT, ΔU = n C_v ΔT, for isothermal ideal gas ΔU=0 Q=W=n R T ln(V₂/V₁), for adiabatic Q=0 W= -ΔU = (P₁V₁ - P₂V₂)/(γ-1), for isochoric W=0 ΔU=Q=n C_v ΔT, enabling calculation of Q,W,ΔU for any process. The Zeroth Law defines temperature through thermal equilibrium but does not address heat flow direction (Second Law) or energy conservation (First Law). 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 =

Ref: NCERT > Physics Book > Thermodynamics > First Law of Thermodynamics Applications

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