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Question: Answered & Verified by Expert
In a thermodynamic process, pressure of a fixed mass of a gas is changed in such a manner that the gas molecules gives out $20 \mathrm{~J}$ of heat and $10 \mathrm{~J}$ of work is done on the gas. If the initial internal energy of the gas was $40 \mathrm{~J}$, then the final internal energy will be
PhysicsThermodynamicsJEE Main
Options:
  • A $30 \mathrm{~J}$
  • B $20 \mathrm{~J}$
  • C $60 \mathrm{~J}$
  • D $40 \mathrm{~J}$
Solution:
1616 Upvotes Verified Answer
The correct answer is: $60 \mathrm{~J}$
$\begin{gathered}\Delta Q=\Delta U+\Delta W=\left(U_f-U_i\right)+\Delta W \\ \Rightarrow 30=\left(U_f-40\right)+10 \Rightarrow U_f=60 \mathrm{~J}\end{gathered}$

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