For an ideal gas undergoing an isothermal process from V₁ to V₂, the work done by the gas is:
An R T ln(V₂/V₁)
Bn R T (V₂ − V₁)
CP (V₂ − V₁)
D(P₂ V₂ − P₁ V₁) / (γ − 1)
Answer & Solution
Correct answer: A. n R T ln(V₂/V₁)
1. At constant T, P V = n R T, so P = n R T / V.
2. W = ∫V₁^V₂ P dV = n R T ∫dV/V = n R T ln(V₂/V₁).
3. (B) is wrong because P is not constant.
4. (C) is the isobaric (constant pressure) work.
5. (D) is the adiabatic work formula.
_Source: NCERT Class 11 Physics Ch 11, §11.7 (isothermal expansion)_
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