QJEEM20Ph5955: JEE Main 2020 Physics - Class 11 JEEM20Ph5955 Solution: A litre of dry air at STP expands adiabatically to a volume of…

Question

Verified Solution • 2025–26 Session moderate

A litre of dry air at STP expands adiabatically to a volume of 3 litres. If

γ

= 1.40, the work done by air is : (3^1.4 = 4.6555) [Take air to be an ideal gas]

Accepted Answer

P_{1} V_{1}^{γ} = P_{2} V_{2}^{γ}

\Rightarrow

P₂ = P₁

{[\frac{V_{1}}{V_{2}}]}^{γ}

= 10⁵

\times

{[\frac{1}{3}]}^{1.4}

Work done =

\frac{P_{1} V_{1} - P_{2} V_{2}}{γ - 1}

=

\frac{10^{5} \times 10^{- 3} - \frac{10^{5}}{3^{1.4}} \times 3 \times 10^{- 3}}{1.4 - 1}

= 88.7 J

\approx

90.5 J

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