JEE Main · 2022 · 29 Jul 2022 · Shift 2 · Heat & Thermodynamics

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A thermodynamic system is taken from an original state D to an intermediate state E by the linear process shown in the figure. Its volume is then reduced to the original volume from E to F by an isobaric process. The total work done by the gas from D to E to F will be

(A)-450 J
(B)450 J✓ Correct
(C)900 J
(D)1350 J

Answer: (B)

Solution

Work done in a P-V diagram is the area under the curve.

For the linear process D→E (trapezoid area):

W_{D E} = \frac{1}{2} (P_{D} + P_{E}) \times Δ V = \frac{1}{2} (600 + 300) \times 3 = 1350 J

For the isobaric process E→F (rectangle, compression):

W_{E F} = P_{E} \times Δ V = 300 \times (- 3) = - 900 J

Total work:

W_{t o t a l} = W_{D E} + W_{E F} = 1350 - 900 = 450 J

The answer is (B) 450 J.

JEE Main · 2022 · 29 Jul 2022 · Shift 2 · Single correct option

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