Skip to content
Login Register

#incorrect statement

100 public questions tagged with this topic.

Heat Transfer Work Distinction and Internal Energy Change

Which of the following is incorrect about reversible processes?

**Internal energy change** ΔU = Q - W, for same initial and final states ΔU same regardless of path, but Q and W differ, e.g., isothermal expansion from V₁ to V₂ ΔU=0 Q=W=n R T ln(V₂/V₁), adiabatic expansion between same volumes ΔU=-W, Q=0, different Q,W same ΔU if same T change, illustrating state vs path functions. Reversible processes are quasi-static and lack dissipation, not involving rapid changes or friction. Option A is incorrect as rapid changes lead to irreversibility. Using first law ΔU = Q - W, W = ∫ P dV, isobaric W = P ΔV, isothermal W = n R T ln(V₂/V₁), adiabatic

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

View Details
Cyclic Processes and Reversibility Concepts

Which of the following statements is incorrect about adiabatic processes?

**Reversibility** reversible process can be reversed by infinitesimal change, no entropy production, quasi-static without friction, e.g., Carnot cycle reversible, irreversible processes involve friction, free expansion, heat transfer across finite temperature difference, entropy increases, most real processes irreversible. In an adiabatic process ( Δ Q = 0 ), temperature changes (e.g., decreases during expansion), not remains constant (isothermal). Option B 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 - T_c/T_h, evaluation yields Temperature remains constant, consistent with thermodynamic laws and energy conservation.

Ref: NCERT > Physics Book > Thermodynamics > Cyclic Processes and Reversibility Concepts

View Details
Specific Heat Capacity and Latent Heat

Which of the following statements is incorrect about an adiabatic process?

**Specific heat capacity** c = Q/(m ΔT) (J/kg·K), molar C = Q/(n ΔT), heat required to raise temperature, Q = m c ΔT, for water c=4186 J/kg·K, latent heat L = Q/m for phase change at constant temperature, fusion L_f and vaporization L_v, Q = m L, e.g., ice melting L_f=3.34×10⁵ J/kg, water vaporization 2.26×10⁶ J/kg. In an adiabatic process ( Δ Q = 0 ), temperature can change (e.g., decreases during expansion), as internal energy adjusts via work ( Δ U = -Δ W ). Option B is incorrect as temperature is not constant. Using first law ΔU = Q - W, W =

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

View Details
Second Law Heat Engines and Kelvin-Planck

Which of the following statements is incorrect about reversible processes?

**Carnot engine** reversible engine operating between T_h and T_c has maximum efficiency η =1 - T_c/T_h, T in kelvin, e.g., T_h=400 K T_c=300 K η=0.25, real engines less due to irreversibilities, second law defines direction of spontaneous processes and entropy increase. Reversible processes require quasi-static conditions and no dissipation, not common in nature where irreversibility dominates. 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 - T_c/T_h, evaluation yields They are common in nature, consistent with thermodynamic laws and energy conservation.

Ref: NCERT > Physics Book > Thermodynamics > Second Law Heat Engines and Kelvin-Planck

View Details
Equation of Continuity and Flow Rate

Which statement is incorrect about surface tension?

Surface tension arises from cohesive forces at the liquid’s surface, decreasing with temperature due to weaker molecular interactions, not increasing. The incorrect statement is that it increases with temperature. As per NCERT, applying relevant law/formula with correct units and sign convention leads to It increases with temperature. This satisfies dimensional consistency and physical conditions given, so option C is scientifically correct.

Ref: NCERT Class 11 Physics, Thermal Properties and Gravitation.

View Details
Universal Law of Gravitation

Which of the following statements is incorrect about gravitational force?

It’s attractive (option 1 correct), follows inverse-square (option 2 correct), and is conservative (option 4 correct). Option 3 is incorrect as it is not limited to Earth. As per NCERT, applying relevant law/formula with correct units and sign convention leads to It acts only near Earth. This satisfies dimensional consistency and physical conditions given, so option C is scientifically correct.

Ref: Halliday & Resnick, Fundamentals of Physics, 11th ed., Chapter 13: Gravitation.

View Details