Thermodynamics
Heat, laws of thermodynamics, Carnot engine
Key Concepts
- Zeroth law: thermal equilibrium defines temperature
- First law: ΔU = Q − W (energy conservation)
- Second law: heat flows spontaneously from hot to cold; entropy increases
- Isothermal: constant T (ΔU = 0); Adiabatic: Q = 0; Isochoric: W = 0; Isobaric: W = PΔV
- Carnot engine has maximum efficiency for given temperature limits
Important Formulae
| First law of thermodynamics | ΔU = Q − W |
| Carnot efficiency | η = 1 − T_L / T_H |
| Ideal gas law | PV = nRT |
| Specific heats relation | C_p − C_v = R; γ = C_p/C_v |
| Work in isothermal process | W = nRT ln(V₂/V₁) |
| Work in adiabatic process | W = (P₁V₁ − P₂V₂)/(γ − 1) |
Quick Tips
- γ = 5/3 for monatomic gas, 7/5 for diatomic gas.
- Refrigerator COP = T_L / (T_H − T_L); heat pump COP = T_H / (T_H − T_L).
- Entropy change ΔS = Q_rev / T; total entropy of universe never decreases.
Sample Practice Questions
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Heat capacity at constant volume Cv of a monatomic ideal gas:
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Answer: 3R/2
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Internal energy of an ideal gas depends only on:
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Answer: Temperature
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In a refrigerator, work done W, heat removed from cold body Q₂ and rejected to hot body Q₁. Relation:
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Answer: Q₁ = Q₂ + W
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Zeroth law of thermodynamics defines:
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Answer: Temperature
Practice Questions
Practice 20 randomly selected NEET questions on Thermodynamics. Answers are revealed after each question.
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What are the key concepts in Thermodynamics for NEET?
Zeroth law: thermal equilibrium defines temperature; First law: ΔU = Q − W (energy conservation); Second law: heat flows spontaneously from hot to cold; entropy increases; Isothermal: constant T (ΔU = 0); Adiabatic: Q = 0; Isochoric: W = 0; Isobaric: W = PΔV; Carnot engine has maximum efficiency for given temperature limits.
Which formulae are important for Thermodynamics in NEET?
First law of thermodynamics: ΔU = Q − W; Carnot efficiency: η = 1 − T_L / T_H; Ideal gas law: PV = nRT; Specific heats relation: C_p − C_v = R; γ = C_p/C_v; Work in isothermal process: W = nRT ln(V₂/V₁); Work in adiabatic process: W = (P₁V₁ − P₂V₂)/(γ − 1).
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