A-LevelPhysicsThermodynamics9702/12 · Feb/Mar 2017 · Q171 Mark

A gas is enclosed inside a cylinder which is fitted with a frictionless piston. [Figure showing a piston in a cylinder with gas, initial volume V₁, external pressure p, final volume V₂] Initially, the gas has a volume V₁ and is in equilibrium with the external pressure p. The gas is then heated slowly so that it expands at constant pressure, pushing the piston back until the volume of the gas has increased to V₂. How much work is done by the gas during this expansion?

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Ap (V₂ - V₁)

B½ p (V₂ - V₁)

Cp (V₂ + V₁)

D½ p (V₂ + V₁)

✓ Correct answer

A: p (V₂ - V₁)

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Topic: Thermodynamics, A-Level Physics (syllabus 9702). Multiple choice, 1 mark.
Source: A-Level Physics, Feb/Mar 2017 Paper 1 Variant 2, question 17.

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