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In the following P-V diagram the equation of state along the curved path is (V-2)²=4aP, where a is a constant. The total work done in the closed path is

Asked in JEE Main 28th Jan 1st Shift 2026 · Work as the Area of a Closed Loop

Figure: Work as the Area of a Closed Loop
Answer: (1) -1/(3a)

Step-by-step solution

Along the curve P=((V-2)²)/(4a).

The curve runs from V=1 to V=3, where P=1/(4a) at both ends, and the

loop is closed by the horizontal line back at that pressure.

Area under the curve: ∫₁³((V-2)²)/(4a) dV=[((V-2)³)/(12a)]₁³=1/(6a).

Area under the straight leg: 1/(4a)×2=1/(2a).

Enclosed area =1/(2a)-1/(6a)=1/(3a), and the loop is traversed so

that the work is negative: W=-1/(3a).

Why the other options are wrong

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