Thermodynamics

JEE Main level, single correct, medium

35 of 190

Question 35 of 190

The pressure of a gas changes linearly with volume from AA to BB as shown in figure. If no heat is supplied to or extracted from the gas then change in the internal energy of the gas will be

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Answer: (D) 4.5J4.5J

Given here, ∆Q=0∆Q=0
From first law of thermodynamics, ∆Q=∆U+W∆Q=∆U+W, where, ∆U∆U is change in internal energy and WW is work done.
We have, ∆U=−W∆U=-W
W=AreaunderP−Vcurve=∫PdVW=AreaunderP-Vcurve=\int PdV
Here, volume decreases, hence work done by system will be negative.
∆U=−W=30×103×150×10−6∆U=-W=30\times {10}^{3}\times 150\times {10}^{-6}
=4500×10−3=4500\times {10}^{-3}
=4.5J=4.5J

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