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Thermodynamics asks very few questions in NEET(UG), and almost all of them come from the same small set of ideas. Learn the first law and the four processes properly and this chapter stops costing you marks. Ten questions below, with the answer key and a hint for each.
What this chapter carries in NEET(UG)
- Usually 1 to 2 questions every year, which is 4 to 8 marks.
- Most of them come from the first law and the four processes.
- The signs are what trip students up, not the physics.
What the syllabus says
In the syllabus (Unit 8, Thermodynamics): Thermal equilibrium and the concept of temperature, the zeroth law of thermodynamics, heat, work and internal energy, the first law of thermodynamics, isothermal and adiabatic processes, and the second law of thermodynamics with reversible and irreversible processes.
Taken out in 2024: the Carnot engine and its efficiency and heat engines and refrigerators.
Taken from the NMC syllabus for NEET (UG) 2026, the latest one published. See the full syllabus, unit by unit.
Formulas you must know by heart
| First law of thermodynamics | ΔQ = ΔU + ΔW |
| Isothermal process (ideal gas) | ΔU = 0, so ΔQ = ΔW |
| Adiabatic process | ΔQ = 0, so ΔW = −ΔU |
| Isochoric process (fixed volume) | ΔW = 0, so ΔQ = ΔU |
| Isobaric process (fixed pressure) | ΔW = PΔV |
| Mayer’s relation | Cp − Cv = R |
| Ratio of specific heats | γ = Cp/Cv; 5/3 for a monatomic gas, 7/5 for a diatomic gas |
| Second law of thermodynamics | a process that would move heat from a colder body to a hotter one on its own is not possible |
| Cyclic process | ΔU = 0 over a full cycle, so Q = W |
Keep the four processes straight: isothermal means temperature fixed, adiabatic means no heat, isochoric means volume fixed, isobaric means pressure fixed.
Ten questions. Give yourself ten minutes.
Write your answers down before you scroll. A question you looked up is a question you have not answered.
Q1. The first law of thermodynamics is a statement of the conservation of
- (a) momentum
- (b) charge
- (c) energy
- (d) mass
Q2. For an ideal gas undergoing an isothermal process, the change in internal energy is
- (a) zero
- (b) positive
- (c) negative
- (d) equal to the work done
Q3. In an adiabatic process, the quantity that stays zero is
- (a) the change in internal energy
- (b) the heat exchanged
- (c) the work done
- (d) the pressure
Q4. An ideal gas is taken through a cyclic process. Over one complete cycle, the change in its internal energy is
- (a) equal to the heat supplied
- (b) equal to the work done
- (c) zero
- (d) equal to the work done minus the heat supplied
Q5. In a process carried out at constant volume, the work done by the gas is
- (a) zero
- (b) PΔV
- (c) nRT
- (d) negative
Q6. For one mole of an ideal gas, Cp − Cv equals
- (a) zero
- (b) R
- (c) R/2
- (d) 2R
Q7. The value of γ = Cp/Cv for a monatomic ideal gas is
- (a) 1.4
- (b) 1.67
- (c) 1.33
- (d) 2.0
Q8. The internal energy of an ideal gas depends only on its
- (a) pressure
- (b) volume
- (c) temperature
- (d) density
Q9. When an ideal gas expands isothermally, the heat it absorbs is
- (a) zero
- (b) equal to the work it does
- (c) equal to its change in internal energy
- (d) equal to half the work done
Q10. For any natural process in an isolated system, the entropy
- (a) decreases
- (b) stays exactly the same
- (c) increases
- (d) becomes zero
Answer key, with a hint for each
| Q1 | (c) | ΔQ = ΔU + ΔW is energy book-keeping, nothing more. |
| Q2 | (a) | Internal energy of an ideal gas depends only on temperature, and temperature is fixed here. |
| Q3 | (b) | Adiabatic means no heat enters or leaves, so ΔQ = 0. |
| Q4 | (c) | Internal energy is a state function. The gas comes back to the same state, so ΔU = 0 and the heat supplied equals the work done over the cycle. |
| Q5 | (a) | No change in volume means no work: ΔW = PΔV = 0. |
| Q6 | (b) | Mayer’s relation, Cp − Cv = R, for one mole. |
| Q7 | (b) | Monatomic gas has γ = 5/3 ≈ 1.67. The 1.4 value belongs to a diatomic gas. |
| Q8 | (c) | Temperature alone. Change the pressure and volume together at fixed temperature and the internal energy does not move. |
| Q9 | (b) | ΔU = 0 in an isothermal process, so all the heat absorbed goes into work. |
| Q10 | (c) | Entropy of an isolated system never falls in a natural process. |
Now mark yourself honestly
NEET(UG) marks the way it marks. Use the same rule here:
- +4 for a right answer
- −1 for a wrong one
- 0 for a blank
So ten questions here are out of 40. In the real paper, 45 Physics questions are out of 180.
If you scored 32 or more, the basics of this chapter are secure. Move to harder questions, not more of these.
If you scored below 24, do not feel bad about it. You have just found out something useful before the exam did. Go back to the formula table above, learn it properly, and sit these ten again tomorrow.
And if you guessed a few and they landed, count those as wrong. A guess that works once will not work in May.
The full chapter, on a clock
Ten questions tell you a little. Forty-five tell you the truth.
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